The Usable Security blog from UC Berkeley has posted the first part of it's complete examinations of optical scan and DRE systems from the big 4 e-voting vendors Diebold, ES & S, Sequoia, and Hart Intercivic.
First up is Diebold. Reading the details of how one votes and the problems they've identified I don't know how anyone can possibly get it all right and cast an accurate ballot.
Particularly scary is how the optical scanner gives you no inkling if your individual votes have been counted correctly. The complexity of the DRE's interface is daunting.
A very useful read for the e-voting interested.