I don't mind it and I'm always happy if someone I know shows interest in it. If a stranger approaches me about it, I'll give them a quick demo myself, but I will hand it to someone I know personally.
I do keep a close eye on them mostly because I use it for work and for fun and if they open any of the key apps that I use for work, I ask them to close it because I don't want to risk data loss or corruption while they mess with it.
Everyone's skin has grease, that's a fact of life. I don't mind it, and if I did, it can be wiped off easily and quickly.