seems to me like obsidians best games are always when they get to use someone elses tech. they clearly spend more money on the game than on the technology. nwn2, kotor 2, FNV, all good or great games, none of which were built from scratch (well maybe nwn2 since that engine was so altered, and yet that was the most troublesome of the three with regard to tech)
then ap and dungeon siege 3 come out, mostly built from scratch by obsidian, and are generally considered mediocre at best.
seems to me, as much as i like obsidian, they are better off improving the work of others, than building something totally on their own.
i really hope they get to make a mini-sequel or spin off of skyrim. and i am super duper fingers crossed that they get another crack at making a fallout game, new vegas is probably my favorite game of the last 5 years.