After using dbPoweramp for years, here is one killer feature that I would dearly love to see added: the ability to skip conversion if the destination file has a newer timestamp than the source file.

I have a large FLAC library, and also maintain a copy of that library in MP3 format on an SD card in my phone. I regularly add new ripped CDs to my library, but it is tedious and inconvenient to always have to take the card out of my phone and put it into my computer every time I rip to keep both libraries always in sync. With this flag I could update the MP3 library periodically: put the card in my computer, fire up batch converter, point it at my entire FLAC library and run an MP3 conversion pointed at the SD card. Tracks that I've previously converted to MP3 won't be re-converted, because the timestamp of the destination file is newer. Tracks that I've re-ripped for some reason will be re-converted as they should be, because the timestamp of the destination file is not older. And newly-ripped tracks will be converted because they do not exist in the destination at all.

(This would be a perfect synchronisation if dbPoweramp could also delete files from the destination that don't exist in the source, to reflect tracks that were renamed or deleted, but I'd imagine that would be a lot more difficult to implement within the structure of dbPoweramp. Just being able to filter on timestamp solves most of the problem!)