Fun, smoother than Etrian Odyssey 2.. I find myself spending a lot of time playing without realizing it.
The game is challenging, although I find it to be less painful than the second game, which I gave up after reaching only the 8th floor or so. One notable improvement is that FOEs (the ridiculously strong boss-like monsters that roam around each floor) provide experience when defeated. This makes grinding your levels up significantly easier, since you can get strong enough to compete with the FOEs on earlier floors and get quite a bit of EXP from them without getting your butt kicked too hard. Each floor provides new challenge; even if you're strong against the monsters on your current floor, the next floor will be tough until your characters gain another level or two. As long as you're on your toes and always keep an Ariadne Thread in your pocket, you'll be in good shape.
The character classes are all new for this game, but are overall fairly similar to classes in earlier games: some are good defenders, some are good attackers, some have magic, etc. How you create your guild and arrange your party is entirely up to you. For each level gained, you get one skill point to spend on abilities or stat upgrades. I like to make at least one of every class and have them hanging around the explorer's guild just in case I feel like switching things up (also, I like to see all the different character artwork). I would highly recommend keeping a farmer around – you may think he's just taking up space there in the back row, but his camping/gathering skills are extremely helpful and make up for anything he lacks in battle. After a certain event, the subclass is introduced, meaning you can have each class learn the abilities of another class.
Battle is unfortunately un-animated. It's all menu based, no real movement on the part of the monsters, and you can't see your party. This is the only thing I wish could be different about Etrian, but it seems like a small sacrifice to the overall enjoyment of the game. It's certainly not enough to make me pass it up.
None of the Etrian games are heavy on plot, but this one has more events than EO2 (unfortunately, I've never played the first one, so I only have the second game to compare to). It's no traditional RPG, in the sense that you play out a story; it's all about the exploration, fighting your way to the next level. For me, every time I turn a corner and find those stairs, I feel a sense of achievement, and excitement to see what the next floor holds. The bits of story I've gotten so far have been intriguing, and I can't wait to see what happens next. If you're not afraid to take a chance on it, I definitely recommend this game- you might just find yourself pleasantly surprised by it.