I agree that it is safe. Just make sure ahead a time that your vet uses Isoflorane (sp?) and not any type of barbituates (sp?). Sorry...I am an horrid speller!
And also make sure that they have a tube small enough to use on you babies tiny throat.
Any spay/neuter horror stories that I have heard involved the owner not asking these questions.
Just rememeber that even though it will be upsetting to you to see them go in for surgery...it is in their best interest if you aren't breeding them. Plus they will forget it ever happened in a few days anyway.
I don't regret for a second getting Sydney spayed. It has made her a much sweeter and loving pet...plus I don't have to worry about ovarian cancer!