They do make excellent games, but you certainly aren't alone in thinking that these games could use longer QA periods..
It's a long time problem with Obsidian and Black Isle..
This is a nice piece explaining why they couldn't release their games "when it's done":
http://kotaku.com/5968952/the-knights-of-new-vegas-how-obsidian-survived-countless-catastrophes-and-made-some-of-the-coolest-role-playing-games-ever
http://www.giantbomb.com/forums/general-discussion-30/is-it-possible-for-obsidian-to-make-a-non-buggy-ga-421349/