I loved Santa as a kid and I'm glad my parents played along for a while. I was disappointed when I found out that he wasn't real but I still love the idea and I cherish those memories.
My daughter is 4 and she loves the idea of Santa, too. I actually don't think I ever explicitly told her about him but through watching Christmas movies and shows she caught on.
The one thing I don't like about Santa is the essential bribe to be good or else he won't bring you presents. I have told my daughter that's not how it works and that there isn't really such a thing as a "bad" kid and that all kids make mistakes throughout the year - that doesn't mean they don't get to enjoy Christmas.
Once she starts thinking about it and asking questions I won't try to push her into believing in him, I'll tell her the truth when she asks for it. But for now there's no doubt in her mind that he's real and I think it's pretty sweet.
I know some people don't like Santa Claus for various reasons but for me it's always been a happy and magical association so I'm a big Santa fan!