I would like to see the option to set a throttle limit on bandwidth used for uploads (optional for downloads). I always find the biggest constraint is Upload speed especially on ADSL services.
In addition it would be nice to see the feature of been able to restart an upload/download from the last paused/stopped position. I know this would require an extra overhead for checkpointing, however many free download products support this capability. There is nothing worse than uploading/downloading a large file and for it to be interrupted and have to start again.
Finally while the product is excellent I feel the stability of the supporting Applications needs to be dramatically improved especially for iOS and Android. I am finding on my iPhone4S (iOS 6) that navigating into a long directory structure frequently causes crashes.
Many thanks and I look forward to seeing these improvements in the future.