I've played a bunch of hours in closed and open beta on three diff chars and it is really annoying doing the same 20 missions over again, and I'm really looking forward to getting to twenty on my three gals and not looking back, but here's pros and cons:
Pros:
It is absolutely beautiful to look at. The score is ok, not as good as Guild Wars, but I turn that crap off and listen to my own music when I'm not on vent anyway. But it is really pretty.
Leveling is reasonably fast without being overly boring and storylines are somewhat engaging. There are tons of side quests. I like the elements they learned in GW and applied in that vein.
The crafting model looks pretty good. There's no limits on how many you can be expert in, but you can only master one.
Gliding is really fun.
Cons:
Flying is not so fun, I agree that not being able to look around without changing flight trajectory is very distracting and I think PvP in three dimensions will suffer because of it.
I'm a little worried that there won't be tremendous differentiation between lvl 50 chars. We all have the same skills, we can all use them all the time and they don't want to make this a loot drop chase to the top to see who's top dog in the abyss, so where's the differentiation. (I admit I may be jaded by my experience with GW's tremendous versatility on that score, but I'm way more jaded by WoW's lack of it, so I worry.)
I don't think they achieved what they wanted to achieve in GW with warring factions being really engaging and adding an element of interest, but I don't think adding an AI controlled faction was the answer either.
I'm scratching my head at why they keep acting like they're really working on GW2 when instead they've been working on Aion the whole time trying to really address the issues that GW brought up. Competing with yourself is usually not the best business model, but who knows. I guess it depends on how flexible they're willing to be.
In sum, if you want to while away your free time in a beautiful environment as a beautifully rendered creature (or beautifully grotesque one,) this might just be the game for you.
I put it above Lord of the rings in terms of friend finding and questing. And DDO has gotten to be so complex with all the crap you need to achieve to get to higher level content (and the shear vacuum of helpful players anymore,) I think I might stick this one out for awhile. I miss the experience of my first couple years playing GW with lots of friends and tons of content to explore. I hope this fits the bill.