I got one this summer and I thought it was pretty fun. I had a few problems though:
-After a few times riding it the bearings on both wheels were making really annoying ticking noises when pressured. I don't know how or why they would take damage so easily though.
-I was tightening the big screw on the bottom and it just split in half. I called and they were good about it, but I got pinned with a $30 shipping charge on the 6 inch x 3 inch box that they sent me the new one in
The thing that bugged me the most was that it was charged to our credit card (which they had on file) without telling me, and I assumed the part would be replaced free of charge due to the problem being in the crappy screw.
-I find the wheels wear down really quickly, especially considering how much I paid for them.
The board seems to be really stable at any speed though, and it only takes one or two times on it to get the hang of it.
Only buy one if you have consistent hills around with no traffic (or ride late at night).
Also, having a rubber wheel on the back and a urethane on the front seems to be the perfect balance between speed and traction (I have never tried with 2 rubber though).
Good luck