The argument that KOTOR2 should have a 20 level limit because it's a d20 game is silly. Blind adherence to rules isn't even advocated in d20 sourcebooks, and there are plenty of precedents for levels 21+ in other d20 games.
The argument that the game should be challenging, on the other hand is perfectly valid. I wouldn't care of KoToR2 had 50 levels so long as the game is challenging and fun the entire time. The original kotor was a fun game, but was stupidly easy (especially if you were a vet of the d20 system in general and understood the notions of dc's, crits, ac, etc).
So rather than argue senselessly about 20 levels being the holy grail for a game to be good, why not just expend all this energy coming up with ideas for how to make the game more challenging/difficult?
Oh, wait, the game is about to go gold, nm
