I've already dropped Deadpool, Astonishing X-Men, and Wolverine (though I may still pick up the Old Man Logan oneshot that completes that story... I just hate the idea of spending $5 on it). I'm considering dropping Cable but it seems important to the future of the X-Titles with the whole Messiah Complex/War trilogy thing. New Mutants, Uncanny X-Men, and X-Men Legacy were almost dropped but they've been improving, so they're staying for now.
X-Force and X-Factor have been phenominal from day one! Love them both.
I'm an X-Men fan above all else, so I take a LOT of crap from them before dropping anything. It took a lot of continuity screwups before I dropped Wolverine Origins, and I gave Whedon's whole run of Astonishing a shot, despite the rediculous delays, then Ellis comes in with the same delays and half the quality, so I finally dropped that one an issue or two ago. And Wolverine himself has just been rediculously everywhere to the point where I stopped caring about him, so after Old Man Logan I just stopped. I didn't care about his book anymore. And having not read Wolverine Origins I have no desire to continue the book with Daken in charge.