Well think the special is very good, but Frank's characters seem Flandersize. Like for example Grover being an idiot, Cookie being a little weird, and Bert more excited than Ernie. I'm not trying to be mean, but to me his characters were kind of out place here.
I think Frank's characters had the best parts of the special. The entire Ernie/Bert subplot was very funny. I'm not sure they appeared in the special the way you claim. Grover seemed usually helpful but clueless. Bert was excited at the prospect of marrying royalty; wouldn't you be? I don't know what you mean about Cookie Monster being "weird."
I guess if there's any problem with the special it's that the characters feel shoehorned into a story that they don't really belong in. That NY Times review does have a point though; they spend so much time to building up the ball, then everything else happens in just under a few minutes. I haven't seen the full special in awhile, so I can't completely judge.
There are plenty of nice things in it though; some of the songs are catchy (Tony Geiss deserves kudos for fitting in that whole name in the Find a Husband song), the costumes are great (like Mumford's wizard cap, that looked awesome) and there's a lot of great funny moments (Grover the town crier with Mr. Johnson, someone scalping tickets to the ball, Ye Old Fix It Shoppee).