I think this is quite possibly one of the best (and most honest) articles I've ever read about the Muppets in the post-Jim Henson era. The genius of Jim Henson is mind blowing. He was a man very much ahead of his time and yet also very old fashioned; I guess you could say he honoured the traditions of the past while embracing the technology of the future. He was even in to things like CGI (experimenting with a digital Kermit) and reality TV (see http://www.youtube.com/watch?v=RPFOixtrUl8 ) years before everyone else. Trying to match or recreate the man's work is pointless. It's like an abstract painter trying one-up Picasso.
I'm a puppeteer, an indie filmmaker (who does film with puppets) and I've written a blog about film and video puppetry called PuppetVision at http://puppetvision.info since 2004. Although I have a lot influences, like a lot of people in puppetry, if it wasn't for Jim Henson and the Muppets I wouldn't be doing what I do.
Personally, as a puppeteer I would never want to take on one of those characters. Even if you're brilliant - and I have tremendous respect for performers like Steve Whitmire and Eric Jacobson who are phenomenal puppeteers - you are essentially riffing on somebody else's work and never, ever going to please everybody.
@UncleDeadly - I don't think it's fair or accurate to say that Steve Whitmire "steamrolled his way into the job upon Henson's death". Every account I've ever heard or read is that he was asked to do the role, and Jim Henson had specifically requested that Steve do so in the event of his death. I have no idea what the politics of that "Got Talent" Kermit appearance were, but I would hesitate to jump to conclusions or make assumptions about it unless you were in the room.