My feelings on the X10 remote thus far have also been disappointingly similar with regards to the sluggish and non-responsiveness.
I am using the Remote Wonder Plus and previously also tried the remote wonder. Both operated in an intermittent fashion and the reception is terrible. I am lucky to get 12 feet. "Through Walls" is a joke - I am lucky to get "through couch 8 feet away".
Battery life is also dismal.
I like the mouse feature, but the rest of the problems create too strong an annoyance... oh well shopping again.
I've always found the MCE IR remote to have a brilliant range. I'd estimate it to be easily 10 meters or more. I know RF remotes can have their uses, but nothing a long USB cable can't overcome
I think marmitek and ati remote wonder are the same.
I have marmitek and have been happy with it - it's x10 protocal IIRC - using custom girder setup.
I loose the mouse via pad - but don't need that for MP - and besides I also have a wireless keyboard that provides the mouse.
RE: range/interference - I found raising the RF receiver up and away from the PC and TV to help alot with range/response. Also - ensure batteries are always fresh. Rechargeables seemed to be worse...