bethesda didnt develop new vegas
Bethesda didn't develop the game, but bethesda did publish the game. I used to work in the industry in QA departments, usually when a game comes out that isn't complete it's because the publisher is pushing the developer to release the game by a certain date or funding for their project is kaput. This being said, it puts obsidian software engineers in a very precarious position for a few reasons. They have to use bethesda's old engine, which as we all saw with fallout 3, was a bit buggy, but bethesda spent all the time they could in refining fallout 3 to release the new gameplay style to the gaming world and it was quite successful. Now, bethesda thought they could probably slack a bit and hire some third party developer to create fallout NV, of which the engine was already created, obsidian just had to put a new template and face on the game. While this sounds easy, it can really be a nightmare for the developers who don't have all the inside knowledge of working with the engine. This is why bethesda would publicly state they were working in alliance with obsidian to create fallout NV.
This tactic to produce more money from a title can be clearly seen with the call of duty franchise, the developers who created the game, infinity ward, only actually developed a handful of the games. Usually treyarch would take over for the crappier versions of the game, and it shows. This is a tactic used by publishers to sell the title and stray from the quality side where they can pay people less money to develop the same title, and people usually buy it, unfortunately, because they don't do research about who is actually making what they play.
My point here is it was probably very tough for the developers to work off someone else's engine, and it probably wasn't the fault of the devs. The OP, i feel, correctly identifies bethesda as the problem, but i don't think it's the engineers' fault. I think it was bethesda's business management team, and higher ups that pushed to get this game out too soon. From what i played that wasn't bugged, i thought obsidian did a commendable job recreating the fallout world and feel, a lot better than i thought they would. I just wish they had more time to refine what they were making and address all the open bugs in their bug database, because i'm sure they're all there, they just didn't have the time to put the fixes in. I probably found more bugs casually playing this game than any game i've played as an end user.
I feel shafted as well, and while the game's bugs has made me an active member in the forum community here, all my time has been spent in the xbox 360 issues forum.
I hope bethesda addresses these issues, and is more aware of future endeavors, meddling with the integrity of one of their top selling game could really hurt the company. I know i will be much more of a conscious buyer next time around and i will go around and read the forums before i'm forced go there because my game saves all corrupted.
This was just a personal insight, i could be wrong about the internal struggle between obsidian and bethesda, but in my experience that's way it goes.