There's no need for another ZOMG Nocturne Rocks! review. So I will focus on the top irritating things in Nocturne
1. Slow pacing
Nocturne is a true dungeon CRAWLER. You spend all of your time in Nocturne making your way through maze-like dungeons. They are all pretty much the same. You go down a corridor. The corridor splits left or right. You decide to go right. You find out you picked wrong and are teleported back to the beginning of the corridor Then you have to go back down the same corridor until you reach the same split again. This time you know to go left. So you start going down the left corridor. Eventually you will come to another split. If you pick wrong again, you will be teleported all the way back to the beginning. Then you have to go back down the first two corridors and make the correct choice. Then you will come to a third split, and so on, and so on, and so on.
That's pretty much all you do in all of the dungeons with only slight variations. (Sometimes you have to make your way around pixies who are stationed at splits in the corridors and if they catch you they teleport you back to the beginning, sometimes you will run into invisible holes in the floor that teleport you back, sometimes barricades will pop up in front of you requiring you to backtrack to the beginning and go a different way, sometimes you will be chased by a demon who will catch you and teleport you back to the beginning of the dungeon/maze if you go the wrong way, etc).
When you enter a dungeon in Nocturne, you are in for the long haul. And towards the end, the dungeon/mazes get quite convoluted. You may find yourself going around in circles if you're not careful. Due to the reliance on backtracking in all of the dungeons, it can sometimes feel like a real chore just to get from area A to area B so that you can advance the story. This makes slow pacing the number one irritating thing in Nocturne.
2. Lack of in-game tutorial/detailed explanation of the battle system.
Nocturne certainly doesn't hold your hand when it comes to explaining important concepts. Sure, most everybody will be able to grasp that fire enemies will be weak to ice spells and dark enemies will be weak to light spells. But, if you have never played a Shin Megami Tensei game before you may have a hard time figuring out which spells are which due to the use of many unfamiliar terms. For example, you may be able to analyze an enemy and discover that it has a weakness to light AKA "expel" spells. But it may take you awhile to figure out that a spell called "hama" is an expel spell.
This is in contrast to games like Final Fantasy where it is fairly easy to figure out that a spell called "holy" is a light spell or a spell called "firaga" is a fire spell. In games like FF it is easier to figure out the system because the names of the spells give you a clue to what they do. In Nocturne you basically have to learn a whole new vocabulary to figure out what is going on. And the only way to learn the new vocabulary is by trial and error. That can certainly be irritating to newcomers.
3. Even garden-variety enemies are capable of one-shot kills.
When you hear people in the forums say that Nocturne is a hard game, they are usually referring to the fact that they were one-shot killed a lot in ordinary random enemy encounters.
In order to be able to set up your main character so that he will rarely (if ever) be killed in an ordinary random enemy encounter you need to be familiar with, and understand the way that SMT battle systems work. This is something that newcomers struggle with, especially at the beginning of the game.
Some people find the process of figuring out a good strategy for keeping their main character alive to be challenging and fun. But since one-shot kills and "high difficulty" get referenced a lot in the forums, this seems to be something that not everyone likes. So it is definitely something that people can find irritating.
4. Bosses require a trial and error approach.
Bosses in Nocturne will generally be strong in a certain element and weak in another. But you won't know what those strengths/weaknesses are until after you are already in battle. By then it may be too late. You may find yourself in a battle where none of your party members have the ability to attack the boss's weaknesses, or where most of your party members are weak to the boss's attacks. In both those cases, you will probably die. Then you will need to go to a previous save point, rearrange your party and abilities and try again.
Some people find it fun to tweak their characters until they find the perfect arrangement to kick the boss's butt. Other people find this trial and error approach to be irritating.
5. No voice acting
The soundtrack is great, however, Nocturne is a strictly text reading game. I like voice acting in my games. Lack of voice work is something that I personally find irritating.
6. The world is drab
The world of Nocturne is very barren. The backgrounds aren't very detailed. You mostly feel like you are wandering around plain corridors in a drab, empty world.
The story is about the destruction of the world, and the lone journey of the main character through the destroyed world -- so the lack of details/colors can be excused/explained away as a conscious design choice. Still, I personally prefer more detail/color in my games.
Conclusion
Well that's about all the irritating things I can think of in Nocturne.
IMO the only major irritant is the slow pacing. If you absolutely cannot stand a lot of backtracking you should probably skip this game.
If you don't mind the slow pace, then you should definitely check Nocturne out if you can find it at a decent price.
IMO a decent price is $30 or under – and certainly no more than $40.00. I know in the past Nocturne has gone for obscenely large amounts of money, so I'm taking this opportunity to discourage people from being sucked in by the hype.
This game just got a fairly large reprinting – that is why I was able to buy it new for $30.00 in the Summer of 2008. That should keep the prices down for awhile. But if the price goes back up, try to remember, it is a good game--but there are a lot of other good games out there.
Actually, all the Shin Megami Tensei games are very similar. They could all substitute for each other if you just want to see what an SMT game is like.
Devil Summoner is very similar in gameplay to Nocturne with the major difference being the use of a real time battle system instead of a turn-based battle system. (The story line and general vibe of the two games is very different though, with DS being a much faster-paced and a more light-hearted experience).
Digital Devil Saga is very similar in storyline and general vibe to Nocturne. However, its battle system is much more streamlined than Nocturne's. The biggest difference being that there is no demon collecting/fusing in DDS.
Of course, if you can only get one SMT game, I would suggest that you just go with Persona 3 instead of Nocturne. (Note: I haven't played P4 yet, so it is possible that P4 may turn out to be the must-own SMT game). P3 has a similar battle system to Nocturne. You collect/fuse personas and equip them in battle. However, P3's battle system is so much more refined than Nocturne's. P3 is also miles ahead of Nocturne in graphics and general game design. P3 is designed so that you can go through the dungeon as slow or as fast as you want. If you want, you can avoid enemy encounters and race to the exit on each level. There is no forced plodding/backtracking through drab corridors. Plus P3 doesn't limit you to dungeon crawling like Nocturne does. In P3 you get to explore the town/school and level up your social links. Variety and faster pacing make P3 the game of choice. Plus, P3 has the better storyline and characters too.
FYI my personal favorite RPG for the PS2 is Shadow Hearts:Covenant. Check out its reviews if you are looking to play an old school RPG with a twist and plenty of dark humor.