does anyone use 100LL av gas ?

AVLL when mixed, will not harm your older engine, however it is bad on catalytic converters and O2 sensors. IE newer engines.
The only issue would be lead build up which should be monitored. Not sure about running it without mixing it, so no comment on that.

AVLL is a viable option (FOR OLDER ENGINES) if you can't get race gas in your area or you don't want to buy the Race-gas mix.

I have logged thousands of miles using both and have no issues to report. Clean valves and no leaks.