Developing a game for PC requires a lot of QA work and it's hell to get it to work on everything. But guess what, a lot of developers out there manages to do that just fine. Having a game that works well on most systems isn't supposed to be some kind of bonus if you're lucky. It's required, no matter how much work it is. And no matter how much you look at it, Sith Lords has more bugs than it should have.
And it's not just the technical problems. There are scripting bugs, AI bugs etc. Are you going to say that it's impossible to get those things right as well?
I won't join the "I hate Obsidian more than anything" gang, as I think the game has more good sides than bad sides. But I don't think you should just let them get by with everything. I don't care if Lucas Arts is the devil itself and made them release the game before they wanted. Obsidian is the developer and is responsible for the code in the game. But then again, this is the people that used to work at Black Isle, so I guess I should have waited a few months before I bougt the game...
Not that I don't think Lucas Arts is most to blame though. I truly despise them for what they did (and combining that with all the crap Star Wars stuff they've tried to fool us with,even if the trend isn't half bad nowdays), they're not exactly my favourite publisher.