These are just my thoughts on everything I have seen so far. Currently in the low 40's and have every area unlocked playing as Haru.
Connection Status
No issues. I know the servers are located on the East Coast and so am I. This is the reason why probably.
Leveling
I really believe that the lvl ranges of 1-16 are a tad slow. I've only really been playing for about 5 days not. 2 days took me from 1-18ish. 1 day took me from 18ish-27ish. The 5th day took me from 28-41. To be honest, I only really felt like I was "grinding" lvls on the first 2 days. The keyword being I "felt" the grind at 1-16ish. I have no idea about the higher lvls still, but I imagine with the replay missions it can't be too too terrible.
Dungeons
I like most of them, and I like the variety of enemies you fight/the environments you fight them in. My only issue was that the scaling of the Manic mode seems a bit off. Like in the earlier lvls I'm getting one shot easy, but ever since reaching mid 20's the Manic Modes have been getting "easier". I know it's from the improved gear and all, but I suppose the bottom line is that the early manic modes could afford to be a bit easier. I don't think having bosses that can one-shot you as a good idea.
Combat
It's fun and flashy. It does a good job of making me feel like I'm in an anime. (nerdy but w/e) I like the skill tree/point system. There is a lot that is right here, and easily the strongest point. I just really wish there was a block of some sort. This is a little bit more of a defensive game, and the dodge helps. But why would a defensive game not have a block? I'm sure there is nothing Gameforge can do about this because on contractual agreements.
Hard mode?
Why is this a thing? It's literally useless. Normal makes sense to do story/unlock new districts. Manic Mode makes sense for lvling purposes. Hard Mode is not good for either of these things. Just take it out.
Cash Shop
It's a bit expensive. Either drop the price of the items or increase the amount of soul cash gained per transaction.
Upgrading Equipment
It is so hard to upgrade a weapon. I fail so much that I don't even want to risk wasting the money anymore. It doesn't seem worth it to me. I know its the natural progression of weapons and all, but at not being capped I don't see why I would waste the money. I think the fail rate should be decreased by a bit, or a form of auto success after a certain amounts of fails.
Energy System
Despite popular opinion, I like this system alot. It's a good way to limit the lvl progression of characters so players can, ya know, enjoy the game. There are so many ways to get energy also, that I'm not sure why it's an issue. I have personally never been out of energy ever. I've been close, but never out. This is even with my longest play time (about 6 hours) in one day. I think it's fair. My main reason for liking the energy system as much as I do is it's a good way to stop meta/hard core players from dusting everyone.
I really haven't done much crafting so I can't say one way or the other. I think that's about all I have to say so far. I'm sure I'll update this more and I play more of the game and see what it has to offer.
My future concerns are:
Crafting will take too much grinding.
What do you even do at lvl 55?
Leveling will slow down too much once you reach lvl 50ish.
Raids?