Balance for the most part has been steady. There have been a couple patches where one or two classes stood above the rest but that was earlier in the Korean patches. The exception is right now in Korea, Warlock is a bit imbalanced but it's a brand new class and there has not been balancing since it's release. It will be tuned quickly.
Lucky for the NA client we are updated to the most recent patch for the foreign versions and are enjoying a lot of balance. Some classes feel stronger than others but nobody is standing WAY above the other and every class is competitively viable. Plus the scene is very young, meaning skill trumps everything at this point.
As with every fighting style game, there will be imbalance here or there and at some point a patch will mess things up for a bit. But its always been addressed quickly. At the worst you will have a class that's A tier and other B tier or C tier classes but never the ridiculousness that some games reach where a class becomes S+ tier and no one else can compete.
I bought a founder's pack just to check it out. I played about 8 hours and I'm done. For me, it feels like I'm playing a super korean version of Tera 2.0 or something. I'm just not feeling it personally. It feels really linear (ie. I run down a road to go to a place and the road is the only option, you can't climb/jump/run up like sides of hills and places you were obviously meant to Buy Blade And Soul Gold. The jumping really high and gliding and stuff is what kind of made me want to play because I loved the gliders from AA so much (stupid I know) but even so you can't glide (fly) over like walls and stuff due to invisible barriers.
Graphics aren't the main thing I need in a game, but I need immersion. This game feels like old school WoW in that there is no grass or bushes or anything, its like barren land with a few mobs there. You can stand in the middle of an area and see everything (assuming no structures are blocking obviously, but things like trees/tall grass/bushes won't block view), which for me, just makes it feel like a game / task - its like walking into a puzzle room and seeing all the puzzles you know you'll have to do before you've even started one. Your character is very pretty but when you move it just feels so .... pre-rendered if that makes any sense. Its like I don't "feel" like I'm moving - I feel like I'm pushing a button and then a model is moving - not sure If I can explain that one