Well, I've enjoyed the cast changes. I think a lot of shows keep the same people around to an unrealistic degree. In real life, people change jobs a lot. In a realistic version of Star Trek, the Enterprise would've replaced its captain and crew maybe once every year or two. In a realistic version of Stargate, the original members of SG-1 would've been rotated off the front lines after a year or two and a totally new team would've taken their place. And so on.
Actually my favorite part of the whole series was the "reality show" period where House held a competition for his new team members. Actually I hate reality shows, but since this was purely fictional, it was a lot of fun.