I used a Cateye Solar in the 1980s that I rigged with an external dry-cell pack using Ns or 123s (can't remember which). I liked it when I had it. And this was only a few years after I lusted after a Pacer 2000 - and the young lady whose bike it was on. But neither of those worked out. At least the Solar lasted for a number of years.

By the time Avocet came out with the 40 and 45, they were reasonably reliable. I mentioned earlier I still use an Avocet 45 as my primary cyclocomputer (for the past 30 years or so), moving the head unit from bike to bike and resetting it to that bike's calibrated wheel circumference (determined with a measured closed course and refined if needed with long checkrides alongside RWGPS). The circumference calibration steps of 0.04" allow for remarkably precise calibration (but not necessarily always accurate, depending on tire pressure and sensor offset from the wheel magnet ring). That being said, sub-0.5% (1/200) accuracy is routine. I used to really like the cadence function, but now that I have decades more riding experience I can "feel" a rough cadence number (within 3-5 rpm) without needing the display. As each unit eventually starts failing after about 10 years or more of service, I switch to the next backup unit I've hoarded away after obtaining at bike swaps and yard sales. However, one design flaw is the battery cover clips are fragile, and on my current 45 it's held on with gaffer's tape - inelegant but functional.