I played NWNs for about five years, the last three spent building and DMing my own world with an eight hour closed session every Sunday. I had the same half dozen players and a few co-DM helpers for the entire period. I created over 500 areas for my world, scripted heavily and ended up using 2GB of modded content customising every aspect of the game.
Divinity is a very interesting prospect but it cannot really be compared to NWNs 1. I've had the briefest of looks at the editor and it seems more like the complexity encountered in the Electron engine (NWNs 2) although without the polish. Having said this... if they were to improve the usability I would be very tempted to give it a go.
The real difference between the two games of course is the turn-based combat. I can't see this working in a Persistent World or massed PvP situation - having to wait your turn would make it too easy to gang up on an individual player - but I think it would be fine for small co-op party play.
