I know one person who apparently experienced some minor recreational effects from Flexeril; well, enough recreational effects so that he'd pay a dollar per pill for them, which doesn't mean all that much considering the sky high price of pills these days; plus I've known people who've paid more than a dollar for fucking Seroquel.
Personally, I've found absolutely no recreational effects from Flexeril at any dose. My friend gave me some for free a few months ago after I slipped on the kitchen floor with a knife in my hand & cut two of my tendons, in the hopes that it would help with the post-surgery pain 'cause of tendons direct connection to muscle. I only felt any effects from Flexeril when I took at least a few times the "recommended" amount, & even then all it did was make me feel really tired but unable to sleep, in a way that was not only not recreational but flat out unpleasant.
Most people say Soma's are the only muscle relaxer worth considering using recreationally.