I have never had a problem lending out my combo provided people ask and treat it with respect. Most of the time it's being DI'd so I ask them to leave the volume alone.
Have had a few times when I've been told I can use someone else gear and then not been allowed to touch the EQ, which gave me a horrible sound
PS. I am currently investing in a new rig to prevent this in the future (and cause my combo isn't very well and needs fixing)