This is not old-school in a good way, and I am an old-school RPGer.
GRAPHICS
The graphics are designed in a mediocre way. I do not care how old they are. Look at the graphics of the Infinity Engine games (BG, IWD etc.), these use old 2D graphics. Why do I still love them? Because they are detailed and well-designed. Avernum's graphics are not well-designed. They are blocky and basic. A 2D sprite game can look a lot better than this. I understand they were developed by a small company, but hey, I gotta judge it for what it's got.
SOUND
The sound was alright, considering the basic nature of the game. I rather liked the combat and spell sounds.
GAMEPLAY
This game was not bad by any means, I just think the game is posing as something it's not. If the interactive roleplaying elements were more complex, I could forgive the badly designed graphics and cumbersome interface. Let me make something clear, my priorities are gameplay first. But graphics are a nice benefit, keeping in mind I said I only care about the detail of graphics, not the age. The game has a great storyline, starting off your character in the weird and unique world of Avernum. The dialogue is great, and the exploration vast. As soon as your characters (PCs) are geared up, you can explore the vast world. There is loving attention that has been paid to the events and locations.
There are many secret areas to explore, and there is definitely an epic feel to the game. You could explore the world finding monsters and treasure, or solve main and side quests. The quests normally involve minimal talking, mostly fetch quests or combat quests. This is where my problem lies. For an action/rpg with exploration, there are much better options available. Play Oblivion, Elder Scrolls, or many other such games instead, you might as well. What's that you say? Graphics don't matter, only gameplay? Problem is, Oblivion and other new games of its ilk, have great gameplay. The rpging is a bit shallow, but they have great exploration, combat, and storylines. Exactly like Avernum. So why make the sacrifice of graphics and interface that you have to make with Avernum? This is my problem, having old graphics does not make your game old-school. Old-school is when your game has something new games do not offer much. If Avernum had more complex rpging, dialogue and interaction, I would love this game. But it does not.
As a lover of old rpgs, I have to say this. Avernum is good, but it does not offer anything you can't get better with other games. My favourite rpgs are ones like Baldurs Gate 2, Planescape: Torment, even Ultima 7: The Black Gate. BG and PsT both had many interesting sidequests with many characters, great dialogue, and many choices. Ultima 7 actually only had one way to solve most quests, but the exploration, attention to detail, and interactivity was unbelievable. For me, Avernum does not cut it as an old-school rpg. The type of action/exploration/rpging it offers can be satisfied better by Oblivion and other such games.