I've been using the non-XP ones for a few years now. They are very good for "quick" tasks like holding something in place while you work on it, and for certain types of glue-ups (they are good for gluing edging onto ply for example - I basically clamp the ply and butt the clamp bar against the edging).
I wouldn't use them for any glue-ups where the surfaces being glued could be moved out of position by the clamping action though as the clamp jaws don't move parallel to each other. I find this problem increases with the length of the clamp, so although I have a few longer ones I invariably only use the 6" ones (but I use them a lot). They apply a lot of pressure too (more than I would have expected) but not as much as a good threaded clamp.
I haven't used the XP ones, but as the style seems similar, I'd wonder whether they could overcome the issues that arise with the standard ones. But those issues are only a problem under certain circumstances though.