Second Best Tie-In I've Read so Far
Now, I haven't read Secret Avengers yet, so maybe that'll take the #2 or #1 spot, but so far the X-Men tie-ins have been a lot better than the Avengers tie-ins. This one works really well to give perspective to some of what we've see in the main AvX series. We get to see into the heads of a few characters and I like where they are going - character-growth-wise. I was shocked that they split up Colossus so soon after Kitty became tangible again, but they are potentially doing some pretty neat things with colossus as Juggernaut. At the very least we get insight into what it was like for Xavier's half-brother to be Juggernaut.
If you're following Avengers vs X-Men but are an Avengers fan (oppsite of me) this is actually worth picking up. It gives some good filler information - especially for Hope.