I bought a Phatmoto Rover while the pre-sale was going on. If you can keep them running and avoid ALL of the problems that lead to catastrophic failure then they're a great bike to own. That being said mine is out of commission at the moment. For the first 500 miles I put on it (after break-in and tight down), it was a dream. Starts up nice and quiet, takes off smooth, and once you've switched the spring assembly with a pin it tops out at around 31. The first problem I ran into was cr@p tires - one patch of slate on the road put a gaping hole in the tread. One walk of shame and replacement tire later, the rear brakes start to go. I check them to see the wear and my heart sank... the pads were completely gone and the metal pegs that hold them together were shearing into the wall of my rim. Suffice to say I don't use the rear brakes any more. The front brake is a 165mm disc but sadly it's not hydraulic. The last problem I had with the bike and reason it's not on the road is that I forgot to perform a simple maintainance check on the rear sprocket. The entire rear end of the bike came to me factory assembled to the frame along with the jackshaft. So I figured they were smart and used red threadlocker. No such luck. The screws that hold the rear sprocket to the hub had backed out and were shearing against the frame making a noise that sounded exactly like the centerfugal clutch did when it was brand new, making me unaware of it until I physically examined the bike.
To conclude, if you know every piece and part and all the specs on them and perform routine maintainance religiously, then this is an awesome bike to own. If you are new to motorized bikes and have never built one before, DON'T. Not unless you like torture that is. If you've built a few motorized bikes before and think you know your stuff, it could be awesome just do your homework. One problem can put these excellent workhorses off the road. I say they're excellent even though they're prone to problems because when they are in tip top shape, they're a dream to ride.