I have an OhShiBoom, I've been using it about 18 months now and love it.
All of the impacts have a reliance on hitting something fairly solid and occasionally fail to go off. But their massive advantage in CQB is that when they go off its instant. The down side of traditional pyro and the timed bfg's are that if someone knows its coming they can get out of the way before it goes off.
In woodland I wouldn't bother with a bfg, mainly because I like having the range a mk5 can give me, you can throw those full pelt into people and they wont hurt. If they went off on them that might be a different story, I've seen one hit a guys shoulder and go off causing no damage other than temporary hearing loss. I've got good 10 or 15m lobs on them from time to time.
My safety pin is on a retractable lanyard which is secured outside the pouch the ohshi fits in but I also carry a spare. At the moment I'm still working through the box of 50 9mm blanks I got but I will be buying the smaller shotgun primers and adapter shortly. My 9mm blanks are held in a pair of bianchi speed strips which I keep on a length of paracord tied to my belt and in my right pocket. If careful when reloading you don't need any tools just put the blank in the adapter, screw in slowly then press the wobble top gently and reinsert the pin.
But 50 9mm blanks and an oshi works out cheaper than 50 tlsfx mk5's. So in my head it's paid for itself. I might even buy a second one shortly but it will be shotgun primers all the way from now on.