If you transfer items between characters, there is a high chance they will simply disappear sometime. This has been brought up on multiple forums, and nothing has been done to correct it.
If you are okay with your most valuable, often one-of-a-kind loot getting permanently erased, then by all means use this app.
Ive lost my highest light level ghost shell, as well as 3-4 Iron Lord Artifacts to this junky software, and it will take me at least a month of gaming to get them back. This app may have ruined Destiny for me, to the point that Id rather wait for Destiny 2 than deal with all the progress Ive lost. Thanks a lot.
PetetNels107 about Destiny 2 Companion, v4.3.0