JDAN:

I have experienced NO downside at all. Small discomfort at first (lasting days, perhaps). Rude awakening when I learned that I'd have to abstain, or use other forms of birth control for the first couple of months (to make sure it took and that any swimmers were expelled w/o a chance to follow their natural instincts). Key question is whether YOU are ready to father no more children. If the answer is "yes", then I say go for it.

One word on reversibility: my urologist had me confirm that I understood that the vasectomy was "voluntary, permanent sterilization." If I had not confirmed that I understood it to be permanent, he would not have done the procedure. That is, DON'T go in thinking that it is reversible.