I've only read the first two in the trilogy, the third not being in stock at work yet (but it's on order and I have a reservation on it). It's weird, this trilogy. It's cliched, slow moving, somewhat predictable and with the wettest heroine in christendom - yet there's something strangely fascinating about it that makes me want to read on.
Agree with you on the age range, although only for the more mature twelve year olds.
Can I also recommend - totally different genre - Celia Rees' Sovay, set in England and France at the time of the revolution and concerning a young girl who turns to highway robbery in order to save her family.