Why on earth should I care about the rollyos created by Debra Messing, Arianna Huffington, Rosario Dawson, or Brian Greene? OK, after that rant, Rollyo looks really interesting. It's better than the Bloglines account (which I found completely overwhelming), because it's easier to manage and filter, but it fills the same information need.
However, in terms of "sharing" rollyos, it's not terribly useful because the rollyos aren't sorted at all! You can "explore" the rollyos, which is a very unhelpful term because you're not exploring, you're searching through the rollyos looking for ones that use search terms that you're looking for.
Professionally, I think I should be looking at book review sites, and this might be a good resource for it. While I'm designing a My Books & Authors rollyo, I think it would be much easier if the search sites were automatically alphabetized while I was editing them, because it would be easier for me to find one or double check that a particular site was part of the rollyo, however I like that the sites included in the rollyo are listed on the page with the results of my search.