I'm 24, he's 34.
For the record, I don't feel like it is, I'm a single mum to DS3 and have always felt like a bit of an old soul. But since I told my friends I've started dating this guy (very recent but I really like him) they're all absolutely shocked and say the age gap is huge.
My parents have 18 years between them so maybe I'm used to it but... Maybe it is a lot? It's really messing with my head!
YABU - too big of a gap!
YANBU - 10 years is fine!