I went from a cheapy speedo to a Novak Cyclone about 2 years ago and it is still running fine with no problems.
The difference for me was night and day. It made the car feel as though it was on steroids. Especially as I race stock class most of the time.
The Cylone may be a little on the Porky side compared to todays new breen of postage stamp speedos but for me the reliability has been impressive. If it ain't broke don't fix it springs to mind.
Yorkie