I had problems with a wireless computer, my HRM interfered with it, and it thought I was doing 17 MPH when I was stationary. The other drawback with wireless is that you need to replace 2 batteries rather than 1.
I found having a cadence readout has probably helped me make the best improvement to my cycling for many years, I just wasn't spinning the pedals fast enough. Not only am I faster now, but my knees are feeling better for it, and I get up hills without tiring myself out so much.
I have a Cateye Strada Cadence fitted to both of my cycles, I did consider using just one, but the cost of the kit for a second bike wasn't much less than the cost of a complete unit, so I bought a second one.
In the 3 years that I've had them, I've done 1000 miles with one and almost 3,000 with the other Apart from strange readings in heavy rain, and changing the battery at about 1,500 miles, I've had no problems.
If you calibrate them correctly, they are within 0.5% of the reading I get from my GPS.
EDIT: The wired model does have an auto start / stop, it starts as soon as a signal is sent to the unit, either from the wheel sensor or the pedal sensor, and stops when the signal stops. You can cycle so slowly that the display stops, but that's down at about 1.5 MPH.
Personal experience with this product.
· 9 years ago