Dislike them, mainly due to presentation. Crystals come across as too New Age-y, the terminology often looks like scientific and medical jargon, and the source of it generally has an implied ring of evolution, or occasionaly out-right said (like with gith).
When the presentation at least meets me half-way, though, I'm willing to give a little. I don't mind psionics as much in Eberron, for example, thanks to the sense that it's coming from the realm of dreams (at least in part) as opposed to any hyper-evolved mind, as well as the fact that psionic creatures like mind-flayers are the result of direct nigh-deific intervention and alteration rather than any kind of silly, time-travelling paragon's of evolution and genetic mutation.
As for the argument about psionics being pure fantasy, well, sure, in the same sense that the Force is. Which also has science-fiction connotations behind it. Mind-powers might not have any scientific basis, but they are strongly a part of the sciene fiction genre, from Babylon 5 and Star Trek to the X-Files and Minority Report. Psionics often is to science-fiction what magic often is to fantasy.
And, like was pointed out with Star Wars, sometimes the only real problem or difference is a matter of presentation.