I'm just getting familiar with OpaVote and am extremely impressed with the system, including its capabilities, simplicity, and documentation (as well as price!).
The one feature I'm disappointed not to see is the ability for a voter to change his/her vote. I can understand that not allowing "revoting" would make it easier to ensure the anonymity that is usually required. But it seems that, at some additional design cost, supporting revoting could be done securely without jeopardizing anonymity. Put another way, votes would not be anonymous in OpaVote's internal data but would be anonymized in the reports that are provided. Is that approach considered too costly or too vulnerable in some way?