i started real slow on burning WMO, like a gallon per fill up, but then got brave. i was in the habit of running 60% WMO all the time for a good while, mixing it before filtering, worked great when i could take an hour every night to do it, then life changed and i'm living in an apartment, so i don't have as much time to spend on it. now i get it when i can, usually when working on whatever up at the parents house cause thats where my system is. i've run as strong as 90%, though at that point its a bit slow getting into the engine and i can feel it starving a little bit. also, its a bit challenging to start with a mix above about 60%, though starting and stopping on plain #2 and switching to a stronger mix while driving avoids that concern.
the ONLY serious problem i ran into on WMO was when i had a bit of metallic debris in my oil supply, which got past the filters in tiny particles. it gathered on the fuel shutoff solenoid on the top of the injection pump and fried the solenoid. it took me a couple weeks to be willing to burn oil again after that, but i got over my fears, placed several strong magnets along the bottom of my tanks and on the outside of my filters, and got right back to burning it.
once you get used to the idea of it, its really not anything to worry about