Yeah the daleks are like really crappy wooden garbage cans with even less manoeuvrability than R2, altough in the new series they can leviate so stairs no longer pose a problem. I think the background is that something happened on their planet which destroyed their bodies so they have to exist inside these wheeled machines.

There's a whole load of links and pictures and stuff about the current series and the next (10th) Doctor
http://news.bbc.co.uk/1/hi/entertainment/tv_and_radio/4395849.stm