I enjoy receiving my folio under my door on the morning of checkout as I can slip it into the plastic envelope that I keep for business receipts and into my briefcase before leaving the room. No need to stop at the desk for it. I look at the emailed folio as a back-up but the issue with that is that it takes several days to a week after checkout (8 days and counting now for a checkout at the Philly Downtown Marriott) to arrive in my In Box.
I see that some hotels are eliminating the paper folio for environmental reasons (similar to the excuse on newspapers). If this is the trend, I would like to have it as an option in my profile to receive or not. Or, if the emailed folio could generate day of checkout that would be ok as well. If Hilton branded properties can get your folio to your email on day of checkout and Hertz within an hour of return, no reason why Marriott couldn't either.