This poses a problem for me, and possibly others though. I like to attempt to read almost all of what comes down my funnel. I have built a priority system already inside of google reader. I have folders basicaly 1 - 10, that ranks the importance of things. For example, I can usually read my folder 1 everyday, 100% of it. As I have time I will read through lower folders.
So, with this system I have done part of what newsblur does which is to help me seek the good stuff. This even works across clients. So I can use the google reader web UI, and Reeder.
I would love to be able to use the newsblur web UI in place of the google reader API, but without the sync it wouldn't fit into my system.
I know that my system may not be something you want to cater to, but hopefully you can understand how for some people google reader sync is very important.
I'm thinking about further integration with Google using Google Contacts (for a Email Story feature), but that's about it.