I becoma a fan right from her debut. Listened to Stars and got hooked by the vocals. Really really nice vocals IMHO. My favourite songs were Stars, Yuki no Hana, Resistance, and the new hit song from the hit Movie, NANA - Glamorous Sky.
The movie is really good. If you actually read the manga, I would recommend you to watch it.
And the last tour DVD [Let's Music Tour] that is coming out this week is awesome too. Managed to catch the TV boardcast. ^^