yeah - I'm struggling with this too.
-VUDU will let you take DVD's and Blu-rays you own, and disc-to-digital into your ultraviolet library by going to a Walmart Store
-CinemaNow will let you disc-to-digital discs youown into your ultraviolet library from home, but it only works on DVD's.
To top it all the list of titles available for disc-to-digital is currently pretty shoddy, so most of my time is spent ripping the disc into an M4V file, storing it on an external hard drive on my mac and watching on the AppleTV's / iPads around the house via home sharing.
What few movies I probably want on the road I either sync locally onto the IOS device before travelling or use those on the rare occasion from Ultraviolet.
Obviously a key expansion area for iTunes disc-to-digital options. I'd pay handsomely for it ;-)
UPDATE: I just checked and the new VUDU Beta allows you to do disc-to-digital for DVD and Blu Rays at home. Still ultraviolet centric of course.