I don't own the Gevey Ultra, but I've had a U-socket for a few months now and it's been an awesome product. Has totally freed up one outlet for me.
If you've ever installed an electrical outlet, you should have no trouble installing the U-socket. It's a bit bulkier than a normal outlet, so space can be tight when trying to fit it back into the wall bracket. I did have to arrange the cabling a bit so it would lie flush with the wall and not have a gap around the edge of the wall plate. But once I did that, no trouble at all.
It's reliably charged a number of items (iPad, iPhone 3 & 4, digital camera, etc) and I've noticed no issues at all. Can't say enough about how handy it is to not have to plug a wall wart into the outlet to charge some electronics.