Yeah, I'm kinda of two minds about the game so far. Now, keep in mind I'm only about 10 hours in, so any/all of this could change, and I could be completely wrong about some or all of it.
First off, the combat, which is the biggest part of the game. It's...not bad. Not great, but not bad. I don't have any problems with how it works in general, in fact I quite like it. This is probably due to the fact that in essence, it's exactly the Musou combat system. Triangle > Circle, Triangle > Triangle > Circle, etc. And I love Musou, so this has been easy to get used to. And the ACE skills are nice too. Not too much to say about them. Dashing/air dashing works rather well, but doesn't feel very "fluid", like rolling and dodging in MH. My problems with the combat come into play when talking about how it "feels", though. It just doesn't have much weight or "oomph" behind it. You rarely ever feel like you're hitting anything. I mean, the combat itself is enough fun that this doesn't become *much* of an issue, but if you're a MH vet coming into RO for the first time, it can be a bit disappointing. I'm also not sure I like just how similar all the classes feel thus far. Usually in games like this there's one or two styles I really like and gravitate towards, and several others I don't like and avoid. However in this...I can't really find any that I love or hate. They're all just...decent. I don't find myself having more fun playing one class than I do playing any other. Which is both good and bad I suppose.
The second thing is the customization. Now, granted, I haven't spent enough time with the game yet to really have grasped the whole system, but my initial impressions are that I expected a bit more from it. Most of the loot feels pointless since a large portion of it goes towards customizations that are entirely cosmetic. Clothing and headgear are basically pointless (aside from the one embedded skill that outfits seem to have), with all the *real* customization coming in the form of cards. Which again is both good and bad. It's nice to be able to make your character look exactly the way you want without worrying about stats and such. But grinding for loot and materials feels a bit hollow when you're doing it for purely cosmetic reasons instead of doing it for new equipment that will make you stronger. Now I know loot is also used to refine weapons, and that's nice. But the fact that the game seems so short on weapon types makes it a bit empty feeling. One of the cool things about MH is all the awesome looking weapon types and variants, and RO seems to largely lack that. The loot tables seem weird, as well. I'm still very early in the game, but I've already found a Bone Staff that GREATLY outclasses anything else available to the Mage at this point in the game. And my mage set is now ridiculously overpowered as a result.
I don't have much issue with the stages or the "repetitiveness" of them like some reviewers seem to. I'm a Musou/MH vet, I'm used to revisiting the same areas over and over again. The one problem I do have is that many of the areas seem very small and narrow. It feels like you spend a lot of your time fighting in small, cramped hallways rather than larger, more open areas. I also find that the camera tends to freak out a bit in smaller areas, sometimes making it impossible to see your character while in the middle of combat. That kinda sucks.
One other thing I should bring up is the AI mercenaries. From what I gather, these were added as a response to players' complaints about hitting a large difficulty wall while playing solo. However, in my experience thus far (I'm at the start of Chapter 4), they don't seem too terribly useful. Their stats are low, their equipment is bad, and they more often seem to serve as meat shields/decoys rather than actual useful fighting partners. I thought that maybe they'd scale up as you progressed through the game, but so far that doesn't seem to be the case.
So yeah, overall...it's taking some time for the game to grow on me, but I'm coming around on it. Slowly, but I am. I mostly just wish the loot gathering felt more important that it does. I've mostly been playing solo, but I have ventured online a little and it seemed okay. Not a ton of lag, mostly smooth. Oh, one other thing I noticed. When using the Hunter and doing any combo ender that involves multiple arrows (for example, the spread-shot one), the game noticeably lags for half a second or so. Like, just completely freezes up for a fraction of a second. Seems like a bit of a weird technical error (I'm on the PS3 version, by the way). I hope this is something that can/will be fixed in the future, since it's a bit jarring.