I knew a guy who said "I like older cars because I can work on them". And he did. Every weekend. I vowed I would purposely never learn how to work on cars so that I would never be tempted get involved in such a tremendous time sink. The worst thing about the hobby is it tends to insert itself exactly when you don't want to do it.
So really, for any given car, if you work on it yourself, you shouldn't be spending much more time than what the shop would charge you for the same work, and, uh, like I said, $90/hr post-tax isn't something most of us sneeze at. (Of course, if you can sneeze at that, good for you!)
that said, right now I'm taking my vehicle to a professional. the thing is, sure, the car only needs something once every 6 months, if you don't count oil changes (which I usually take in, just 'cause it's worth twenty bucks to not deal with the oil) - the thing is, where I am now, maintaining a garage would cost me more than just paying to take my car in. So yeah, it doesn't always make sense.