I looked into one of these before since they are pretty neat and would be handy at times. The parking thing really isn't that big of an issue if you really want one. If the hill you park on is steep enough your bike will still creep in 1st gear anyway. I have a buddy I ride with that keeps his bike at another garage and the driveway is about 45* downhill. When I meet him there I turn my bike off while he is getting ready, put it in first, stay seated on the bike and it still creeps backwards if I don't hold one of the brakes. Well, just throw a little wheel chock in the saddlebag or pull the front brake lever on and use a little wedge of some sort to keep the brakes applied or do both if it makes you feel better. Remember some of those old quads or trikes that used a spring-loaded clip where you would squeeze the lever then push it in place to lock, then release the lever and the hydraulic pressure holds it in place til you squeeze harder to release it? A wedge would do the same thing so that problem is fixed.
Problem #2 ... This is a big "IF" and most likely would never happen BUT could so never say never. You are by yourself out in the sticks somewhere with no cel service and stop to take in the sights, have a smoke and a drink, take a break, whatever ... turn the bike off, leave the radio on kick back against a tree and fall asleep only to wake up and find your battery doesn't have enough balls to crank over the engine. No troubles, I'll just give it a little push, jump on, pop it in 2nd or 3rd, let the clutch rip and I'm good .... oooops, I forgot .... that doesn't work with a centrifugal clutch!
Problem 3 ... All your jealous buddies will rag on you for your "girly" auto-clutch that they really wished they had, but they blew their dough on more chrome do-dads to clean instead.
Last but not least is the price ... Are you willing to drop around $800 for it? I know that's not an issue for some and that's great, but some of us don't have that lying around to blow.