Craig234: it it worth buying here also? For example the novellas listed here aren't listed on Steam. It's only $5 on sale.
While I bought multiple releases of the game (D2:ED, DKS, D2:DC), and have bought DRM free versions of games I already had retail or Steam releases of, if the only reason you are looking at the GOG version is the extras, the DD and BD pdf files are part of the D2:ED
fansite kit (19MB), and the soundtracks can be gotten from the composer's website:
Kirill Pokrovsky (IIRC Steam has the 2 anthology music compilations, rather than the soundtracks). The LMK tech demo is exclusive to GOG (bonus from the launch promo GOG did for D2:DC), but it is also a bonus for Divine Divinity and Beyond Divinity.
The extras would be slightly more convenient to have on GOG, though, and the installer is presumably a little easier to backup (have not tried the Steam game backup function).