There is a bit of a drawback in the system, in that it can be hard to keep your ballot secret. However for that to be a real problem then the guy paying you for your vote would have to stand by the scanning machine and watch carefully. In my experience there is just some old guy who hands out ‘I VOTED’ stickers. :)
I am curious about the statement that some voters’ party IDs were known; this is an open primary state.
Once Franken takes office, all three major candidates will have held that Senate seat at one time. :)