I have one.
I think it's great. OK, a little bit more work as you have to push the cutter across, but it does mean you can be very accurate. I have one with a 1/12 arbor. The rear wheels fit very snug, so very good. The front tires have a little play, which means taking some care to make sure the wheel is mounted in the centre before cutting.
There is absolutely no play on the cutter and it's sliding mechanism, so I know every cut is the same (and perfect).
The only slight downside I have with it, that it only comes with an on/off switch, so to reverse the direction of the drive motor I have to swap the power leads around.
For it's low price, I definetely recommend it.
1/12 V-Dezign Carpet Ripper 4.0 / GM Genius 75 / GM Pro 10.5 metal / LRP 5400 50c
1/10 Tamiya 414JJ / LRP Sphere TC Spec / Nosram Storm Evolution 10.5 / CS 5200 50c saddle pack