When I saw the film (which I though was better than 1 and 3 but not quite as good as X-Men 2) one of the stand-outs was the score. Upon buying it it is soon apparent that there are only two major themes on this album, the Magneto theme and the X-Men: First Class theme. But don't worry as these two themes are worth the price alone.
These are two very different themes. If you want to hear them in the sample then go for track 1 for the X-Men theme and the last track for the Magneto theme.
The first track "First Class" is all about the violins and key changes and is superb. About half way through the tempo builds up with some drums and electric guitar and then the sweeping strings make a come back by the end of the track. Excellent. This theme is repeated a couple more times throughout the album, to best effect in tracks 11: X-Training and track 19: X-Men.
The Magneto theme raises its head briefly in the second half of track 2: Pain and Anger and then builds to a superb crescendo in track 5: Frankenstein's Monster. However the best track on the album is 20: Magneto, where the Magneto theme is given full reign, with sinister strings, thumping base and strong electronic sounds throughout (track 19 segues perfectly into this track.)
I would have preferred one or two more themes, tied to different characters, but I have been listening to it solidly for a month now, so it must be doing something right.
Definitely worth the money if you like the samples.