That's the spelling that I was first introduced to when I was a kid, and I've always loved it. Plus I think it makes the pronunciation more apparent for someone unfamiliar with Arthurian names.
I think it's usable. It's one of the more recognized Arthurian names and it's not too hard to spell or pronounce. I've never had great luck with Ygraine combos, but here are a few:
Ygraine
AliceYgraine
FionaYgraine Fionúir
Ygraine
LinnetYgraine
MatildaYgraine
NolwennYgraine
RowenaYgraine
Lavender