Honestly, I'm not a big fan of it. Especially whenever it is established in canon that the characters are straight and are in a relationship already (like Tony/Pepper is in the movies). But this piece is just so well-written, the descriptions are beyond amazing, and characterization is given extreme importance that I simply accept what is written without question. Everything is of the highest quality and even when established relationships come to an end (Tony/Pepper, Bruce/Betty, etc), they are handled realistically and the characters tend to leave on good terms regardless. That's part of the reason I'm willing to read this. No one is taken horribly out of charcter simply to establish a new pairing. Everyone is so
Other reasons I read this is because of the action scenes. If you provide a well-written action scene that gives almost everyone a chance to shine or to make a contribution, while keeping everyone in character and within the capabilities already established (No God Modes here), then I'll read eagerly and happily. Adding in the X-Men is just icing on the cake. If you have two teams of disfunctional and collective outcasts coming together, you know that there is nothing but Pure Awesomeness
in the future. The story is still being written, but I definitely see great potential for this piece.
So, in summary, I'm not the biggest fan of slash, but keeping everyone in character, adding amazing action scenes, tossing in the X-Men, and simply producing astounding quality means that this is worth reading regardless.