While still an enormous fan of the original Armored Core, lack of intuitive gameplay prevents the series from moving up.
I am, and always will be, an enormous fan of the original Armored Core. AC 3 was a disappointment for me in that it was so difficult to play that I, turning to casual gaming rather than hardcore (life demands my time), was unable to play past the first few missions. Armored Core 4 also becomes difficult very quickly, although the main problem here isn't as much the difficulty as it is the interface. A few issues that I noticed immediately. First, I rented AC 4. Which means I didn't get a handy instruction booklet. This means that during the tutorial you're told to do a variety of tasks including overboost, shoot, go to spot x, etc. The tutorial doesn't tell you how to do any of this and I couldn't figure out how to access the information to find it. I basically had to mash buttons to figure out how to play. Not the best way to do it.
The second thing I noticed was how sloppy the menu system is. I just wasted an hour of my life trying to figure out what the idiot who designed it was thinking. It's the least intuitive interface I've ever used in a video game, and I've played some bad video games. You're not given any instruction (once again, button mashing) and you're let loose on this lackluster interface that leaves you frustrated and wondering what the hell the different menus do for you. To make matters more confusing, some of the menus you'll enter are useless and have different functions than the previous games. Veterans will remember when going to the garage meant you were you going to purchase parts. In this game, the garage function is prominently displayed at the top of the screen with a button kindly mapping you to it, yet the garage is just a useless "look at my robot" menu that shows your AC in a dark tint.
Discovering how to customize your AC, which is one of the most important features in this game, is difficult and time consuming. Customization involves entering the ACSIS menu (no I don't know what that stands for) selecting assembly and scrolling through parts that say "data only". You may select it to add it to your schematic and once you've selected everything for your AC you can exit, save your schematic like that and try to exit to the main menu. The problem with this is that you can't auto default it back to what it was before tinkering and the idiot who designed this didn't bother to put the pricing on. So if you go over budget you won't know until you're ready to exit. Then you have to go back and do time consuming modifications. Even worse, you can't just see a list of items to buy or sell like in previous Armored Core games. In this one you have to scroll through, one by one, which makes comparisons difficult and annoying.
Many of the interface controls are so clunky that it consumes a large amount of time just to setup your AC. Some of the things in this menu STILL don't make sense to me. Like being told I had access to about 7 new schematics, and yet the only one I can find is the starter one (you'd think these new schematics would be available under 'Schematics', but think again). Combat itself was fun, but because of the difficulty in customization I only tried out a couple different combinations. It was fast paced and interesting, but got difficult very quickly. I recommend renting first if you're a fan of the series or if you want to try it out.
For the right person this game may be a lot of fun. For me, I wish they would stick to the original formula that hooked so many of us over a decade ago.
TL;DR - Menus are clunky and difficult to use, makes it difficult to customize. A lot of wasted time on menu system, short intense combat, gets difficult fast. Recommend renting, may be a great game for the right person