I've heard her as Furukawa Nagisa for the first time and still think she was impossibly great. And right after Clannad I began watching Higurashi and was shocked with the difference between cute, warm-heart Nagisa and yandere Rena. However, I love both.
She has so much range, it's really hard to tell. She does great as Rena, creating an unbelievable difference between her moe- and scary-moments. And of course both of her Nagisas (Clannad and Strawberry Panic) are gret, but the roles I like her most in Zakuro from Otome Youkai Zakuro and Selnia from Ladies vs. Butlers. Like I posted on her profile: her tsun-mode outbeats Rie Kugimiya's by far, at least for me.
Hope she returns from hiatus, soon.