The Brazilian election machines produce no paper receipt for the voter, nor any paper trail for a recount. There's no good way to audit an election result. Already this is a nonstarter for most election reform advocates.
In any case, at present it's up against something thrown together with Ruby on rails.
Front-end: "vote counted!"
Back-end: vote redirected to /dev/null!
It's not immediately obvious to me how to make such a system transparent enough to convince the losers that they lost honestly. Cryptographic schemes may be able to solve it, but I think it's an open question whether they'll be convincing and secure in practice.