Hi...  Some thoughts.
1 J13, check the post by theprawncracker above yours, there's a link there to see Kermit and Piggy's appearance. 

2 Some of the performances I liked.  Tony Bennett was cool as always, his new Christmas CD is on my checklist, it'll be a perfect present for Johnny Fiama.  Miley Sirus, if it weren't for her mega overexposure hype, I'd actually kinda like her as a recording star.  She comes across as a little glam country, I liked her rendition of Rockin' Around the Christmas Tree, considering that song is a classic for another recording star who preceeded her who had a similar singing style—Brenda Lee.
3 Kermit and Piggy's appearance itself...  It was okay.  Piggy got in a smarky shot at Kermit claiming he was jealous over her drooling over Harry Connick Jr., who hadn't been included in Letters To Santa.  But rully, I felt it accentuated the problem I have with the frog and pig's relationship.  PM me if you want to know my stance on that, I feel it'd be better for private talk.
BTW: After the Muppets' appearance I switched over to CBS to keep watching Rudolph the Reindeer.  Never seen that one before, my memories are only of Jack Frost and Happy New Year Rudolph!
That's all I got.
Oh, and Stephen Colbert's appearance made me laugh as Al Roeker picked up on a line Colbert delivered in his show earlier in the week.  You have to have seen it to get the injoke.