I recently bought a used drum machine off of eBay for 60 bucks. It's a Boss DR550 and I'm very pleased with it. It allows me to compose and I use it as a metronome (sounds a lot better than one) for practice.
I don't know much about the latest models, but this one fit my budget and serves me well.
I bought a ZOOM MRT 3 in April and love it. You can use presets to arrange entire songs with intros, fills, etc. $99 new American Musical Supply. I also bought a power adaptor and they make a footswitch.
Its great for pratice and recording. It sounds realistic enough to work live, too, but a real drummer is really the only way to go live.
I have a picture of my rig in my sig. You can see the drum machine there.