I think Disney has really nailed the right tone with this special. It really does have that classic Muppet Show feel. I am pretty skeptical of anything Hollywood does today, especially when it involves sequels and reboots and such, but I think they have pretty much gotten it with this one. The opening bit with Rowlf and Kermit made me laugh out loud within the first minute or two, so that's a good sign.
That being said, I just don't think I can get past Kermit's voice. It just takes me right out of the action. I know Vogel is trying hard, and I know he has gotten better, but as someone who grew up first with Henson and then with Whitmire, it just still feels off to me. The two "gold standards" for the Muppets, to me, are The Muppet Show and The Muppet Christmas Carol, so one with Henson and one with Whitmire. That's what I consider the absolute best of the best of the Muppets.
I don't know if I can really, truly enjoy a Muppet production when I am constantly feeling distracted by the voice. Maybe that's a shortcoming on my part. I do wish them well, and I hope this succeeds, but I just can't get into it like I would previous Muppet productions.