Raze_Larian: Technically the disk version has more bug fixes, but if you install the disk patch on the download version you will most likely loose support for resolutions higher than 1024x786 and widescreen aspect ratios. If you are playing at a lower resolution, anyway, then you can try the disk patch, if you wish (don't know if it could cause other problems).
I'm not so sure about what would happen if you apply the 1.34 patch to the GOG version, but 1.34 does have UNOFFICIAL support for widescreen resolutions. Just open '..\Divine Divinity\Run\config.div' in a text editor and note the resolution variables. Change them to a widescreen resolution. Voila!
The cutscenes and the main menu (New Game, Load Game, etc...) will be anchored to the top left of the monitor instead of nicely centered, but the gameplay seems to work just fine. I have NOT finished the game that way, so that's just initial impressions.