I've been using this for a while, it's very convenient. The worst thing, though, is the metadata. If you pop a DVD into your Media Center PC, an XML file containing metadata will be written to a DVDInfoCache folder. Trouble is, it'll almost always be incomplete, and Media center won't know what XML file to use for the ripped DVD's.
To make Media Center understand, you need to place another XML file called a DVD ID file into the folder to which you ripped your DVD. That DVD ID file contains an ID that points to the proper XML metadata file in DVDInfoCache.
I wrote an application a while ago that you can use to edit the metadata for all XML files in the DVDInfocache folder in a convenient way, add cover art to your ripped DVD folder, and automatically write the proper DVD ID file to your ripped DVD folder so that Media Center knows where to find the right metadata in DvdInfoCache.
I've never really finished or documented it, but it works, in a way. If you're interested, you can find the VS2008 project (C#) here.
Feel free to edit to your wish. You'll need to give the proper DvdInfoCache path in app.config, and a bunch of stuff probably isn't translated, but hopefully you'll be able to run with it. Remember that you need to place the original DVD in the media center PC first in order to let it generate the DVDInfoCache XML file.