In Pegasus's local "Copies to Self" folder (the default location for copies of outgoing mail), it very sensibly shows the recipient rather than the sender in column 1 (even though, as in all other folders, the column-header says "From"). Is there a reason why it doesn't do the same in IMAP folders called "Sent"? It would be very helpful to be able to sort such folders by the value in the "From" column -- but only if it shows the recipient; it's pretty useless sorting such folders by sender when the sender is the same (yourself) for all emails in that folder.
Perhaps this is something the development team for the beta 5 version could consider?