I have found that the several wireless ones I have observed on my bikes or the bikes on friends and relatives bikes were flawed in a way that I found a problem when on long tours. Strangely they always seemed fine when around town at home. The main problems were:

• Miles logged when parked near a neon sign. Since I often lean the bike against the front of a little store or diner this was a problem when on tour.
• Bogus readings near power lines, electric fences or other interference.
• On some you need to push a button to wake it up when it goes into rest mode overnight.

None of these ever bothered me much at home, but on tour where I rely on both the total for the whole trip and the total for the day to keep track of where I am, it was a major inconvenience.

I have used a bunch of different ones including Cateye and Planet Bike. Some models from either were OK, but I like the planet bike ones better. The Planet Bike ones I have had use a single button. One short push to toggle display modes and one 5 second push to reset trip mileage, elapsed time, and so on. The few display modes are well thought out and simple to navigate and read.

I agree that fairly simple is best. No need for a plethora of features. The main things are current speed, odometer, and trip odometer. I do like to also have a thermometer and current time though. Other stuff like elapsed time and max and avg speed are ok if they don't get in the way or complicate operation. I find that they don't on the Planet Bike, but do on the Cateye models.

I find the thermometer on the Planet Bike to be a big plus. I is surprisingly accurate as long as you are moving.