Rated 4 out of 5 stars

Sadly not completely perfect.
Seems Stylish Sync has problems if your stylesheet collection is too big...
I submitted a bug report over at google code, so if you'd take a look I'd certainly appreciate it!

This review is for a previous version of the add-on ( 

But there's nothing really to be done here, as explained in http://code.google.com/p/stylishsync/issues/detail?id=1#c1 .

You might try one of the suggestions there.

It's a limitation by Mozilla's sync servers.