Wow, this thread began in 2013 by CK?!??! Yikes.
Anyway... I saw it twice over the weekend, second time in giant (IMAX-ish) 3D. A few of the sequences were pretty spectacular in 3D, but for the most part it didn't make much difference.
While I certainly enjoyed the movie, I felt like it arrived too soon after Captain America, and thus did not come across strong in comparison. It's a shame because I love these X-Men characters more, but the Avengers movies are just so much better written/produced and thought out.
I think ultimately the biggest mistake they made, and I don't consider this much of a spoiler (but be warned just in case you are a real stickler), is insisting on having the 4 Horsemen be a set of otherwise well-known good guys. It might have sounded good on paper to compete with Civil War, but from a writing standpoint I think it was a huge mistake. It forced them to have to devote a significant amount of time "developing" plotlines and story arcs for how these characters are recruited and become horsemen...
In the comics it was cool and interesting to see the transition from Angel to Archangel/Death, but in this series Angel was a nothing character (in fact doesn't he appear in one of the original trilogy?) and so the transformation has zero impact from a character standpoint. Psylocke, one of my all-time favorite characters, was pretty much a complete waste. I think they would have been better served with just some badass evil horsemen and then introduce Storm and Psylocke differently as good guys. They could have ran a similar Magneto storyline without having him be a Horseman. Oh well.
All that said, there are plenty of excellent moments, and a couple as I mentioned definitely worth seeing on the big screen (and 3D if you like 3D). The second audience I was with seemed pretty happy with the movie (applause and pretty much everyone stayed through the end credits) so YMMV.