If I had to tie blood knots on the stream, I'd never have time to actually catch fish. I just started using blood knots to tie my own leaders, but I'll stick with the surgeon's while stream side.

For the folks just learning the surgeon's knot, the knot's strength completely depends on seating it correctly when you tighten it. I've found the best method is to pull all four ends until the knot is just about seated, then pull only on the two long ends. And as with any knot, test it before you fish it.