If your destroying blade temper or rounding off tips on any power sharpening system... YOU'RE NOT DOING IT CORRECTLY. The negative comments on power sharpening seem to be from people who just don't want to sharpen any other way than traditional, or haven't taken the time to learn correctly. It's not that hard to learn.
I use a Kalamazoo 1x42" belt sander, and I've done everything from keychain size knives to 24" machetes. Even Stanley knife utility blades... just because. The Kalamazoo is not the top of the line, but works just fine at the price point. Been using it for about 6 or 7 years. Good selection of belts for 1x42. I use abrasive belts, linen belts with CBN, and leather belts with compound.
I have a Work Sharp, not the Ken Onion model. I've used it for scissors and ceramic blades with diamond belts. Works fine, just not as good as the bigger 1x42, for my uses. As others have stated, if you follow the instructions and pay attention, it will do the job. Having said that, I have fixed a couple of blade tips for a buddy who didn't pay attention.
You are NOT going to ruin the temper on a blade unless you're not using you head. If you go slow enough across any belt that you blue the steel, you're not doing it right. You're certainly not going to change crystal structures or lower blade hardness, by using a power system correctly. That's just plain BS.