For me there is a discernable difference in my mood, my outlook, my demeanor, when I'm riding regularly. For me (and of course YMMV) it's almost completely transformative.

Last night is a perfect example. I hadn't been on my bike since Thursday, couldn't commute yesterday, knew I couldn't commute today, my stress level is high, I'm missing my kids while they're on vacation, and when I got home the weather was nice and we had no plans, so I decided to ride and wanted to really get after it.

Mapped out a ride that had a few hills in it, and did loops of that ride until I had covered 18 miles in total. Got home, showered and really felt like a changed person. It wasn't a mammoth effort or a deep retreat into the pain cave, but it was taxing physically. Not sure I experienced endorphins, but when I got home and after I showered I felt like a fog had lifted from my mind, I wasn't cranky, I just felt better.

My commute is 12 miles one way ... so I don't think I feel endorphins after a commute. But I know a morning commute wakes me up nicely and gets my motor (physically and mentally) humming. And I'm less crabby. And I'll agree ... there's a rush to riding and interacting with traffic and having to just be mentally alert for a commute.