First of all, 5 more minutes and we would be hearing a crack...
I've always wondered, is it as good as getting blown by someone else?
Nah, after a bit your spine gets used into the position, so uncurling needs to be done a little carefully So far, my spine is still intact XD
And for me, autofellatio is just a little lower on the pleasure scale compared to someone else doing the sucking... Cause the underside of my penis is more sensitive, but autofellatio leaves me with my tongue working the upper-side.