I've written about Graffiti a bit here and I think it is an awesome platform. Without making any code changes at all I've been able to implement a blog, an ecommerce site (more info in the form of how-to and examples coming soon) and something new I've been working on the last couple of nights that I'm not ready to share yet. Graffiti is flexible and extremely easy to use.
Everyone I have talked to who has tried it completely agrees. I have a couple of friends who were considering creating their own mini-CMS system tailored to a specific kind of site they were building, but have decided to go with Graffiti instead because it just works. Actually, I've heard a similar story from a couple of different friends now. Another developer friend finally got around to publishing a site that he'd been thinking about building for a while because Graffiti made it so easy that he couldn't think of a reason to procrastinate any longer.
If you have not tried Graffiti yet, go download the free* Express Edition to experience Graffiti for yourself.
(* = free for non-commercial use only and some other limitations/requirements)