Does SPF really work?

Intelopment writes: "My Domain name has recently been used a lot as the REPLY field by some inconsiderate spammer and my ISP has suggested that I consider using the Open SPF service (http://openspf.org/) as a way to stop spammers from using my domain name for their REPLY field. From what I can tell it requires the receiving mail server to actually participate in the SPF service, which is where I get my doubts. Does anyone have any experience with this service? Does it work? Are many ISPs using openSFP?"