Wait, Santa's not real? ;)
Neither one of my stepsons was upset to find out the truth - if anything, they felt very grown-up and clever when they figured it out. I remember being the same way when I figured it out at 7 years old. I don't know anyone who was so devastated to find out about Santa not being real that it scarred them for life and made them not want to "lie" to their kids. Believing in Santa is about believing in magic and to me, that's part of what makes childhood wonderful. Kids generally stop believing when they are ready - sort of like they realize it's a part of their childhood that they are ready to leave behind but will always have fond memories.
As for my 4 year old, we do the whole Santa thing - visits and pics with Santa, making a wish list, writing him a letter, leaving cookies on Christmas Eve, the "Elf On The Shelf" reporting back to him every night. I do tell her that Santa only brings a few things and the rest are from Mom and Dad. And that Santa can't bring her everything that she wants since he has to bring so much to other kids everywhere. I figure that will make it easier to explain other things to her later, like why we donate toys and clothes for children and families in need - Santa can't do everything.
I understand your ambivalent feelings, and you should do what feels right to you, but personally, I think not letting your kids believe in Santa is really letting them miss out on a lot of fun.
ETA: My cousin was one of those kids whose parents did not allow them to believe in Santa - she's now 46 years old with kids of her own and she feels as a kid she got ripped off, as far as a "normal" childhood that allowed for magical thinking as opposed to reality-based thinking from day one. As far as she is concerned, she missed out on an essentially part of childhood. So you might have to think about which will devastate your child more - letting him believe and eventually he finds out the real deal, or never letting him believe in the first place.