I'd say to get one with a separate sprayer for the top rack.
The ancient Tappan dishwasher my parents have only has the sprayer on the bottom. The dishes need to be pretty secure, and they can't be touching, otherwise you'd get constant clanking as it washes, because the pressure needs to be high enough to get the water all the way up to the top rack.
I'll try to remember to check the brand and model of mine when I get home. It wasn't terribly expensive at all, and most of the construction is plastic. It's well over a year old, possibly 2, and it's still going. It's also a hell of a lot quieter than the Tappan washer, though that's not saying much. That old thing was audible anywhere in the house. The one I've got does an adequate job of cleaning, at least with the stronger Cascade detergent. (I was surprised to learn that there's "no-prewash" dishwashing detergent. What the hell's the point of a dishwasher if the dishes would need to be prewashed?) Sometimes I'll do a second quick-wash cycle though with no detergent, as its regular cycle doesn't seem to do enough rinsing to get the soap smell off of plastic things.
Edit: Amana. Model#: ADB1500AWB3