I got into the beta this weekend for Neverwinter, and played it pretty consistently for two days. Overall, this is no DDO, but it was a fun game. What surprised me is how a lot of the mechanics are so similar... here's my breakdown.
Similarities
Both games involve a central city hub.
Dungeons are instanced. Dungeons are about the same amount of fun and interest.
You can have hirelings, and they are just as stupid as DDO, though useful at times, just like DDO.
The community is still full of the same mix of annoying trolls and normal people.
Both are trying to squeeze you for more money.
Graphics in Neverwinter are about on par with DDO (which is pretty pitiful for a brand new game).
Both are action-MMO's, meaning that there is no auto-attack, and require mouse clicking to do basic attacks, and you supplement with hitting abilities from a hotbar.
Where Neverwinter is better
I feel like the action is more compelling. You can't attack while moving, and many don't like this, but it does stop everything from being a run-and-shoot kitefest when you have ranged attackers in the group. Standing still gives attacks a real feel of weight behind them, and I found myself not missing the ability to move one bit. With a wizard (which is the only class I played), you simply stop attacking for one brief second and teleport to a different location when mobs are coming after you.
Wilderness areas are not instanced and can have lots of people playing in them. Some may not like this; I am a fan of this type of play which is seen in most other MMO's as well.
Abilities are more dramatic. (more eye candy perhaps, but also just fun and exciting to use).
Dodging is a really fun mechanic... you see certain places light up in red and you know to get out of there!
Wizard's don't even attempt to melee. Their mouse attacks are ranged. I like being able to cast without thought of conservation of SP. I thought I wouldn't like this initially, but I gotta say, there is nothing more annoying than running out of SP in DDO and either carrying around a stash of pots, paying real money for pots, or just being deadweight on the team.
I did a PvP 5x5 capture the flag match, and thought that was a good time. I don't even bother with PvP in DDO, but I will play it regularly in Neverwinter.
There are events held every hour, which are all listed nicely on a home page.
The foundry (player created content) has great potential.
Where DDO is better
Multiclassing is awesome in DDO and customization is so much more interesting. You have some limited customization in Neverwinter (and at later levels which I didn't see, perhaps there is more). However, for people who just pure class everything, I think Neverwinter is just as good in customization.
I am not crazy about 4th edition rules. Neverwinter lacks the feats and skills of DDO.
DDO has deeper game play, more things to click, more spells to cast, more types of damage to both inflict and protect yourself against... buffs and wards seem largely non-existent in Neverwinter. No clicky items in Neverwinter.
True rezzing to keep a good toon going... I love this part of DDO, and think that more MMO's should do it.
My summary:
Neverwinter is fun and I will play it and probably not do it completely free-to-play, meaning money will be spent. It is a fresh breath of air from the same old DDO content. But I don't see it becoming the multi-year obsession that DDO has been for me. Ultimately for me it comes down to character customization. What draws me back to DDO is not the content, which I am rather sick of, but rather that there is always another type of character to try out.