I agree with Vaughan's First Class being the best of the lot, but I don't know what I think of his work as a director otherwise (Layer Cake was ok but felt like a Guy Richie retread to me, Stardust was a lot of fun but missed the sheer magic of the book, though I'm not sure anyone could have done better, Kick-Ass was a movie I deeply hated, but again I find the comic book pretty awful--I suppose Matthew did remove some of the rapes.) On the other hand I love most of Singer's early work, and love the first two X-Men an awful lot -- the first film's surprise success largely brought back the concept, after a brief hiatus, of a decent movie being made from a superhero comic and really jumpstarted, for good and bad, the last 12 years of those movies.)
So I'm giving Singer the benefit of doubt, though I agree that his last films have shown zero real inspiration. Vaughan is still apparently quite actively involved (he's also a producer for the upcoming new Fantastic Four which makes it seem that the rumours of Fox hoping to do what Disney is doing and tieing together the Marvel movies they own is true.)
As a huge fan of all those 80s X-Men stories by Claremont, I'm really excited this is based on Days of Future Past, though, unlike many internet fanboys, all the changes (ie making Wolverine the main character it seems) don't really bother me. As they don't mess it up as badly as Ratner's take on the Dark Phoenix story did in X3 (how I wish Singer had done that film...)
The trailer is pretty uninspiring but it's an early one, so... And while there are gonna be some major continuity issues in joining the early ones and First Class, that doesn't really bother me anyway (the comics have huge continuity issues too, as did the awful first Wolverine movie which I'll happily pretend was never made.)
The viral video campaign does show the Sentinels--I hope they have more.
http://www.youtube.com/watch?v=OXgCZJ2ERyo