My dd could talk clearly at 9 months. But she wasn't advanced - she was jus a bit of a freakishly early talker. She couldn't walk until she was 17 months - she just put all her development energy into talking. By the time she was 3, everyone had caught up with her, and she is now a bright/average 12 year old.
It is fun when they talk early though - and it's brilliant when you're at the supermarket and they say something and people look round, thinking "Who said that?" It's a bit like being a ventriloquist!