I was pretty much expecting an exploitative mess from this movie, but it isn't. It's cute and fun, with a lot of quite attractive set and character design (I loved the CGI Irontail's whiskers) and some likeable new characters. The plot is a fantasy well within the typical scope of a classic Rankin-Bass holiday special, wthout feeling rehashed, tired or dated. I seem to vaguely remember Jack Frost being a hero or narrator of one of the more minor specials, and found it amusing that his successor was a villain. Even the songs are okay.
On the weak side of this Easter flick: it trots out every but-this-is-MY-generation cliché, sometimes overtly appeals to trendiness and cheap laughs (like Irontail's 'real' name, an intriguing and legitimate plot question wasted on a kindergarten-level gag) and there are a few inconsistencies with the original. (Primarily, Antoine has de-butterflied and spends the movie as a caterpillar.)
But I think the average nostalgiac adult can watch it safely without gagging, and probably even enjoy it. And the kids should be enchanted.