I finally got around to checking out the new Harry Potter tonight and (embarrassingly) it was the first 3D IMAX movie I've seen. The movie was good but I think my eyeballs could do without 3D or IMAX.
Harry Potter has seen a pretty curious progression over the years. The first three movies were stellar. They made me feel like a kid again and all the magic and good-hearted adventure were buckets of fun. The fourth movie was good, but like a teenager's life, seemed to get more complicated to the detriment of the movie. Since then it's been rather dark and depressing (movies 5-8). I guess that's the way the books felt, but the movies seemed to lose their charm when the kids grew up whereas the books didn't tail off until their disjointed conclusion. I guess what I'm trying to say is that being a kid is more fun than being an adult, but I suppose that isn't exactly news.
Overall, definitely worth a viewing, though you might opt for the regular version as the only thing the 3D IMAX version seemed to add was vertigo.