It's usual the contacts between the computer and the mount that let you down. My last Blackburn had this trouble every time it rained a bit. But the last straw was a recent heavy rain ride which has stopped the buttons from working.
I now have a Cateye Cordless.
Cateyes are usualy pretty good compared to most and a pretty safe bet.
That Velo 8 looks like a good choice, I nearly bought one of those when I bought my cordless.