Frankly my first reaction was ''Uh, what?''. I started thinking about it though and I now believe that it's a great move.

 In case you didn't know ZeniMax is Bethesda's parent company. In other words, id is now under the same roof as the creators of The Elder Scrolls and Fallout 3, which could mean great creative advances if the two companies start working together. And also, id (who was always independent and was relying on selling each of their games individually to publishers) will now have strong, consistent backing from a good publisher.

For example, the one problem I have with Fallout 3 is that the shooter aspect of it quite frankly sucks. Bethesda told us that you could play the whole thing as a shooter when they were selling it and that was just plain false. The shooting was barely playable on consoles and mediocre, though usable on PC. They could ask for some of id's expertise to tighten up the shooting, making the game much better.On the other hand, as good as id's games have been, their stories have never really wowed anyone and thats one thing Bethesda does pretty damn well, meaning that Doom 4's story might actually be good.

I'm not actually expecting any of the advantages mentioned above to be noticeable by gamers for a little while. Both developpers have had a pretty full schedule for the next couple of years before the deal was done. But I see nothing negative that could come from this. Worst case scenario: nothing for us will change. Either way we're getting good games.