I have a cheap Planet Bike one on my Jamis Coda. Just speed, time, miles ridden, average speed. It works fine.
I have a Cat Eye on my road bike, but it's wired. It has cadence, but no other fancy functions. When we want to know the grades, Steve wears his Garmin HR monitor. We have tried 2-3 wireless computers and they never work! Mine would always interfere with my husband's or something else. One time I was going 203 mph according to the computer!
So, we went back to the wired.
I don't do any mechanical stuff, so I can't comment on installation. I think the Planet Bike one was a relatively short installation for my husband, compared to other ones he's done.