I'd just get Complete because Mysteries of Westgate is almost impossible to find otherwise. It's not very good, but still. Might as well get it.

Not sure, but the fact that the premium modules are still not available indicates some form of problem. I'd simply assumed a rights issue...

If I recall correctly the NWN1 modules were done in a hurry, since when they released to the public the (final) tilestes used in said modules, they said they were not compatible with the premium modules since those used a preliminary (something to do mostly with walking path changes) tilesets . Maybe GOG is slowly reworking the premium modules so when they released them they use the finished tilesets :) OK, I know it is wishful thinking, but this is Sparta ... I mean GOG ^^;

I've played through Pirates of the Sword Coast, and a little bit of Infinite Dungeons without running into any problems. (As well as Kingmaker, but that's a given)