Trilarion: The old downloader as long as it works is a bit more convenient for just downloading the installers in my eyes (less clicks,
directly starting from browser).
I personally don't consider the need to use the browser in tandem with the legacy GOG Downloader as a benefit. You have to log in twice (through the web browser, and the Downloader client), and it just isn't very intuitive that you have to initiate the downloads on a different application where they actually will be downloaded. So in that sense I consider Galaxy as a simpler method to download the installers, you need to use only one application for it, not two.
Ok GOG Downloader did have one definite advantage though, you didn't have to click all the files individually, but just one metalink which would add all the relevant files to the download queue.
Trilarion: What I hope is that some day before 2020 Galaxy will as good as gogrepo.py, with keeping installer archives up to date and everything.
Realistically speaking, I am not expecting that to happen for two reasons. First, GOG probably prefers that people download stuff only on need to use basis, not that they routinely download everything they've purchased, several times (whenever the installers are updated).
Second, their main development efforts are on the Galaxy side of things anyway, and the offline installers (how easy it is to download them etc.) is the second priority probably.
I'm fine with that though, as long as they don't try to actively block third party utilities like gogrepo from working, and that they keep the ability to download and install the games without Galaxy possible. Most users probably rather download only when they intend to play, I guess.