xa_chan: I'd love an optional client.
Why? Because I have a huuuuuuge backlog, both GOG and Steam, and finally I realize that I only play Steam games, recently. Why? Because I set the Steam client to launch when I start my computer and from there I have an immediate overlook of my game library.
And my GOG games, patiently bought, installed, one by one, their icons are in a "Games" folder, which I now seldom open. So, for the sake of my GOG games, please make a client!!! ^_^
Yeah... good point.
Also, developers love the steam infrastructure. For instance, they love in a software's alpha/beta phase the capability to push updates directly to the users. Prevent in the bug/issue feedback case the problem "What version you had run? Updated to last version???!"
One of the reasons why many games now come first as steam version... GOG, please provide a similar infrastructure while being DRM-free and completely open.