I had a 450d and used it for a while. It was a good camera but I replaced it with a 50d and was much happier. Eventually, the 50 d was sold and I now shoot a 5diii. I sometimes think I should have kept one of the APS-C bodies to take advantage of the crop factor, especially when shooting birds or wildlife.
Today, there was a charity "walk" at our local zoo. Since I am a guy carrying "stuff," folks assume I know how to take a photo (guess they have never seen the ones I delete
). A group of folks stop me and asked if I could take a group shot with their camera. They handed me a Rebel (I actually did not notice which one) with a kit 18-55 lens. I took a few shots (it was st on the green box but after couple, I switched to AV to get a better DOF). I do not want to get into a "camera snob" thing, so take my comments for what they are worth. But, at that point I remembered using the 450d and remembered why I upgraded.
So, it depends on what you are looking for. If you want something that is inexpensive and want a camera that, should it get broken or stolen, will not be an huge loss, and a camera that is better than a P&S with the ability to use lenses you might have for other bodies, then go for it. I think I would get frustrated and wind up not using the 450d after having it a little while.