I find this white mdpv to be ok.
Yeah, it's certainly not worthless -- got 250mg about ten days ago and am nearly at the end of the bag.
First day with the stuff was pretty disappointing -- did half a match-head-size bump (yes, I'm the sort of idiot who
still hasn't bothered to splash out on a set of scales) and was rewarded with little more than an unpleasant and jittery caffeine-type buzz, which faded in a few hours' time. Vaped a bit the same day and got a pretty intense rush, but it only stuck around for about four seconds.
Am now up to a couple of generous bumps per day and am thoroughly enjoying it (though plan to quit for a bit once my current stash runs out). As many have said, it's definitely a subtle thing, at least while you're getting used to it -- the general effect for me at the moment is approx. 1hr of light (but somehow
real and sort of un-forced & 'authentic') euphoria, peaking around 30 mins. after the dose, followed by 2-3hrs of pretty strong background stimulation and, occasionally, some pretty small-potatoes visuals (reading a book or like watching TV, my peripheral vision suddenly decides to darken/lighten itself pretty dramatically -- sort of fun, but hardly
psychedelic, duuuude.). I've read a few reports recommending MDPV as some sort of gray-area super-Ritalin; personally, I can't imagine doing any serious work on this stuff. After the yummy hour of power, I'm generally just
too fucking wired -- not to a physically unpleasant level, but I'm definitely not up to concentrating on anything really productive. (As luck would have it, I'm on an extra-long holiday at the moment. Return to m'studies will, if nothing else, probably curb my

for this stuff a bit.)
All that said, I have found this white stuff really good for one thing: slow, close reading. My experience with stimulants is like two or three lines of shitty speed at some teenage house parties about five years ago. Still, I'd have expected a slightly jacked-up reading speed, if anything. Not so with this stuff, at least for this pertickular guinea pig: trawling through some pretty fucking mainstream (though, like Craig Finn's Berryman, "critically acclaimed and respected") lit. fic. turns into a pretty slow and drawn-out activity (I keep reading and re-reading and re-re-reading seemingly insignificant sentences), but my critical senses come out ultra-sharp -- I notice things that I'd probably just skip over sober and quickly convert them into coherent 'points'. Best of all: these aren't the sort of retarded literary-philosophical ideas I have when I'm drunk. Looking back on them the next day, they seem just as good.
Moral of the story: whatever this shit is, I'm enjoying it, and wouldn't hesitate to recommend it to others. One (perhaps slightly worrying) point, though: I've never found it even remotely aphrodisiacal. Given the numerous reports of debauched all-night wank sessions on the flaky 'tan' stuff, I find it pretty hard to believe that the respectable, white stuff I'm inhaling is actually the same substance. Whether or not random-powder-X is actually any more risky than 'confirmed' MDPV (considering how little anyone actually knows about the latter), it's obviously not a
brilliant idea to be shoving this shit up your nose all hours of the day. Still: in moderation, it's a few v. cheap hours of crisply and precisely altered perception. Bring on the Parkinson's.