My '08 66 RC3 ended up being returned after needing three replacement uppers (awful creaking under load). The first fork had new lowers fitted too, to deal with excessive bushing slop. These are both problems which plagued the '08 and '09 66 range. The fork was a replacement for an '07 SL ATA which spent more time with Windwave than on the trails.
I'm now running an '09 Fox 36 RC2 which is an absolute dream.
EDIT to respond to your update: I don't know if either of those issues applies to the 55, so all that may be irrelevent.