Probably a little too late for me to review this, and in spite of having yet to see the special in full, I still feel like I can unashamedly give my upfront opinion on it ...in short, I didn't really like it. In long, there's sadly worse I can say about this than there is good. I watched most of this on Thanksgiving with my dad (who likes Gaga) and he became less enthused about this than I was. Perhaps that awkward viewing experience is a factor to my cynicism, but I digress.
Overall, this special felt lazy and rushed in more ways than one, right from it's opening number. I know some have complained about Gaga's skimpy outfit here, and I do agree in principle with arguments to that: the Muppets not being strictly kiddie kitsch, performing similar acts on the Muppet Show with Raquel Welch, and so forth. But, I would argue that there's a distinct difference between that episode's well-choreographed sequence with a Muppet spider, and this special's equivalent: just Muppet characters swaying and dancing around Gaga like a tribe while she stands and sings... whoopee!
The Muppet scenes were also pretty weak. While it was a nice surprise to see Carl (the Big Mean) again, that whole audition scene just looked like the puppeteers ad-libbed a buncha stuff and later they framed the subplot with Kermit and Scooter around it. They had the feel of the DXD bits, except less funny. For the most part, the characters were unusually slow and stale in terms of performance, to the point that some of the jokes, even ones that were meant to be bad, flopped; especially Ram-a-lot (UGH!). Having read some of the Jim Henson biography during the holiday week, it took a quote of Henson's for me to notice what exactly was wrong: "These puppets are not just characters up there telling jokes. If you just stand there and tell jokes, the whole thing will die." That's really all it was to me, just the Muppets telling jokes and letting them die. Not much in the way of actual character. I don't know if this was a weakness in Jim Lewis's writing or if it was lost in execution, but it just didn't work for me.
I could honestly prattle on about other gripes I had with this special (Gaga's "acting", lack of Muppet/guest-star interactions, and that tasteless comatose line from Gonzo), but I'm assuming that's already been talked about. I really don't want to continue being a whiny "things-were-better-back-in-my-day" type of fan, but I'll conclude by saying the Muppets have done better holiday specials (as referenced in the opening montage), and in the end, I was more thankful that I watched all of the Muppets Take Manhattan on TCM and I witnessed less of this. Simply put, this was not the best the Muppets have to offer, even by Disney's standards.