I had cadence on one of my bikes, and then I put the Xtra on it and never got around to replacing it. I've got theclock going in front of me and I know that left-right-left in one second would be 1.5 times per second or 90 rpm; if it's 1-2 that would be 60... so I can calculate when I need to and get an approximation.
I also don't handle wires too well... one of mine is on the fritz and I've no idea why. (On the other hand, the distance between my wheel and the handlebars is too much for wireless and I don't really like them anyway 'cause thery're so much less dependable - they give max speeds like 60 mph.)
I kinda like keeping things simple myself.