Xilisoft DVD Ripper Ultimate is the most complete DVD ripper made by Xilisoft. It comes with all the functionality of the "Platinum" version, with a few more additions. For example, it allows you to crop videos, add and adjust watermarks, edit video effects (brightness, contrast, etc), add and set multiple soundtracks, and it comes with a few more options for taking image snapshots of your DVD movies, namely the ability to set the picture quality and capture interval. The feature that I like most of all in this "Ultimate" version is that it lets you preview the conversion process and compare it with the source video. This is often not found in DVD rippers.
Other than the new features listed above, the application looks and works like both the "Standard" and "Platinum" versions. You will find a nice interface which is intuitive and good-looking, a lot of conversion profiles sorted in different categories and by device, and the pane where you configure advanced conversion settings.
Xilisoft DVD Ripper Ultimate works very well and it is packed with features. There is a feature comparison list on the website that might help you decide whether you need this version or one of the cheaper alternatives.