First of all i think that problems mostly are due to yourself.
If you are somebody who are very careful abouth playing not too rough, pushing buttons and keys with respect and treat your equipment well (flightcases) your stuff will bring you less problems.
Here is my list of problems for the last ten years:
* Gem WS2 - Buttons replaced several times
* Gem WX2 - used abouth 500 gigs@5 hrs worldwide. Only mechanical problem with floppie drive - replaced.
* Roland G800 - Several frozen ups, updated 2 times and problems with an additional hard drive that caused problems with the power board. Fixed after 3 visits at Roland repair centre.
Pitch bender replaced after using it just a few times.
* Roland G1000 - CHEERIO!!! No problems at all after gigging with this machine abouth 300 times.
* Yamaha PSR 8000 - Right tweeter replaced, several buttons did not respond and recently contact rubber strip of the keys were wear out (replaced by myself). The buttons prolem is the scariest of all, the reliability of this board decreases enormously.