The exploration alone, while not as fulfilling as the one in Gothic 2, makes the game worth playing. It's completely unfair to place it in the same cesspit as Arcania, Forsaken Gods, Risen 2 & 3.
Core-wise, yes, it tried to bite more than it can chew, but they managed to make a game that, when properly patched, is genuinely fun to play. Gothic 3 is not that bad and most non-core issue (bugs, excessive lensflare etc) are long gone thanks to the Community Patch. It's been a few pages of arguing which PB games are good and which are shit and I am yet to see any of the G3 Underground step up so I will be the member of our minority to make the obligatory 'Gothic 3 isn't that bad' comment: