Yep, I've been running a 60 this year and didn't notice anything wrong with it.
It was running right to the edge though, so we fitted a 70 at Assen. The 70 leaves about half an inch of tread to the edge of the tyre, so maybe less chance of losing the front?
I don't think any of us are good enough to really notice the difference. I think the 70 is probably the better one, just from a physics point of view.
[Edited on 18-5-2006 by domski]