I recently bought the Primos Stray Cat decoy. It has a much more realistic motion than either the Sit N' Spin or the Mojo Critter. It has the bungee-corded tripod legs, but they clip into a plastic retainer instead of the failure-prone rubber arrangement. It comes with extenders, also bungee-corded, for the legs. The cat-butt's tail (the decoy) fits into the motor head like a hex bit, as others have mentioned, this is a better arrangement. Motor/drive noise is minimal, and is growly enough that it doesn't seem to bother anything that comes in close to it. The great forward/reverse motion of the motor shaft means the drive gears make a noise that's not nearly as mechanical sounding. I've had one curious raccoon sit in front of it and stare at it as though he was trying to figure out which end to bite. I wasn't after coons, so I spooked him off before he decided to try a taste test.
The hex shaft on the tail is, unfortunetly, not a standard 1/4" hex so making alternative decoy "tails" meant filing down appropriate sized aluminum rod to fit the hex retainer on the motor. Not a big deal.
The ICOtec e-callers use a pulsed contact closure to control decoys, and the Stray Cat didn't work on the GC350 that I tested it on. Again, for me, this wasn't a big deal. I've simply built an interface that allows me to use any decoy system on any caller system as well as some homebrew remote control systems. The remote for the Stray Cat has about a 40 or 50 yard range, which is sufficient for a lot of setups, but I need more range and flexibility than any of these things offer, so I spend a ridiculous amount of time and engineering effort on better systems. In all honesty, I think these companies should be doing this instead of pumping out gimp products that Chinese factories will make for peanuts.
I do think the Stray Cat has better potential as an effective decoy... the motion it produces is a lot more conducive to making your own custom shafts and covers for it that actually mimic real animals than the simple spinning motion of the others.