mondo84: To bring it back to the topic of the thread, with people being so used to Steam updating games which have just come out, I can't see as many people buying 10 GB AAA games from GOG, since these tend to have such updates/patches.
It ultimately comes down to a trade-off (not the only trade-off, but the one regarding new games on GOG):
DRM-free vs. Auto Patching
DRM doesn't really have anything to do with auto patching. They can both exist in the same product, unless someone feels that none of the Steam games in this list support auto patching?
http://www.gog.com/forum/general/list_of_drmfree_games_on_steam/page1 Another example would be e.g. the _optional_ Humble Store client for Android games. You can still download the DRM-free apk packages, even if there is also an optional client which can do both the downloading and installing for you, and checking also if the installed game is up to date. Kind of like the current GOG downloader, only with even more functionality.
So your question should have been "Client-free vs. auto patching?". You can have even both, like Humble Bundle Android games offer. Or, like many PC games in the past have offered both in-game autopatching, and also a way to download and install the patches separately.
It only may become the problem if the client/autopatching is the only way, like shown with the "Rise of Nations autopatching system went offline for good, and no official offline patches ever released" case.
EDIT: Ok, maybe you were just talking about current situation, ie. if you choose to buy a DRM-free game from GOG, then you choose not to have auto patching. Just wanting to make clear so that no one feels adding optional features (e.g. in a form of client, which GOG already has) would automatically be DRM. Heck, GOG could have cloud saving and achievements too, even without DRM!
Nevertheless, I am unsure though how much the client really matters in the end. Even if GOG had an auto patching client, would the die-hard Steam extremists who require a Steam key for everything still opt to buy from GOG?