I've tried it. I start low and slow with new substances, so it took a few times to get the dose high enough to feel much. When I did, it felt pleasant but minor. I stayed up all night reading a book.
But then, the next three days, I had a terrible, splitting headache. Whenever I tried to sleep, I had moderately lucid dreams, but with a weird sense of terror where I couldn't focus the lucidity on anything but trying to wake up, which seemed extremely difficult, although in reality I would only sleep for short periods at a time.
If it weren't for the headache, I'd give it anther try to see if I could get control of the dream part, but the three day headache was totally not worth it.
My reaction was the most extreme of anyone I've personally talked to. Most people just feel kinda good, some people get kinda sick, and some people get headaches, but they're usually short-lived, not the three day fuckall I had to deal with.
Oh, also, I've heard of shitty headshops selling spice (synthetic cannabis) and calling it kratom, which is dangerous and crap. Make sure you're getting the right thing. It should be a bitter powder you have to choke down in some liquid. Online and IRL herb shops should be fine--it's pretty well know these days.