I like Two Worlds II a fair bit. I'm not having many of the "bugs" that people are pointing out, but I don't doubt they are there. To me Two Worlds II is a VAST improvement over the first, so ignore anyone coming in here and saying "based on the first one...", what they have to say it totally irrelevant in this case. It's NOT an Elder Scrolls game, nor is it trying to be an Elder Scrolls copycat, so trying to compare the two series' game play is futile. It'd be like trying to compare an MMA game to Street Fighter.
There are no classes in TWII, you can build your character up in any way you want. The leveling is done by experience points like most RPGs.
If I had to be honest, and compare my enjoyment of TWII and Oblivion, I'd say I'm enjoying Two Worlds II right of the box WAY more than I enjoyed Oblivion straight out of the box.
You can backtrack to previous islands. Some are pretty damn big, other smaller.
I don't think it's out where I am yet so can you tell me if the voice acting is better? I found it so horrendous in the first one that I wasn't able to go very far at all (it's one of my pet peeves, and I couldn't ignore it in TW), but I've heard good things about the sequel - but if the VA is that bad again, I'm afraid it's a deal breaker for me.