I'm keeping them at original quality. I'm a little bit anal when it comes to picture and sound quality and knew I'd not be happy if I compressed them hence only getting about 200 saved in 1 Tb. I did only rip the movie off the disc though, if I want to access all the menus and extra features I'll dig the disc out of the attic.
My Hi def collection will remain as optical discs.
One movie I did have to compress was Lord of the Rings, it seems that the limit on DVD Fab is either the 5Gb or 9Gb max size, so when I combined the two discs of the extended version it maxed out at 9Gb which turned out to be 85% compression per movie. Watching the movie it has very slight black crush otherwise it looks pretty good. I'm going to re burn it and join with a different program. My wife and friends didn't notice the reduced quality.
I'm watching them on a 42" LCD with HDMi connections through a 7.1 amp.
In short if you spot picture discrepancies when watching hi def media the quality loss will annoy you, if you don't it's fine.