Using gpg is not so awesome. Obnam uses gpg. Since Obnam invokes gpg in batch mode, if you want to have a passphrase, you have to use gpg-agent, which at least for me took more effort than I found reasonable to set up on a GUIless server.
Furthermore, all the crypto config depends on gpg defaults or your gpg.conf. Whether this is good or bad depends on whether you are OK with gpg's defaults that are chosen for a non-Obnam use case and whether you like tweaking gpg config.
While figuring this out, I started wishing that Obnam used libsodium instead of gpg to avoid configuration and especially gpg-agent. (libsodium didn't exist when Obnam was created.)
Furthermore, all the crypto config depends on gpg defaults or your gpg.conf. Whether this is good or bad depends on whether you are OK with gpg's defaults that are chosen for a non-Obnam use case and whether you like tweaking gpg config.
While figuring this out, I started wishing that Obnam used libsodium instead of gpg to avoid configuration and especially gpg-agent. (libsodium didn't exist when Obnam was created.)