Reports surfaced to day that Harden had turned down a 4yr/$52 million dollar extension offer from the Thunder. He was asking for 4yrs/$60 million (which he would definitely make on the open market). Thunder still had control over Harden as he was only set to be a restricted free agent next Summer, but Thunder GM Sam Presti decided now was the time to make the move.
Presti is one of the best GM's in the game, so expect him to not stop at this move. The Rockets won't be good any time soon, so those "significant" draft picks will hold a lot of value (Wouldn't be surprised if one of them wasn't the Toronto pick acquired for Lowry this Summer). Presti can move those pics for another impact player. Jeremy Lamb has been getting rave reviews for the Rockets since being drafted this past June. Bold move on Presti's part, but we'll have to wait and see what else the Thunder do.
For the Rockets their GM Daryl Morey, also very well respected in the game, has been searching to cash in his chips for a star for quite some time. He didn't land Dwight Howard, but Harden is a great get on their part. Rockets still have a lot of work to do, but at least they have an all-star now.
It is worth noting that even after the lockout and with the new CBA rules, the Lakers were able to add Dwight Howard to their payroll despite already having Gasol, Nash, and Kobe's monster contract, while the Thunder were not able to retain their young core. I'm fairly certain that Harden would still be on the Thunder today if they played in a bigger market. The lockout definitely didn't fix the whole haves and have nots dichotomy in the league.