Steam version of Legend of Grimrock carries some Extras from GOG - Saving Content

Excerpt: "If you purchase Legend of Grimrock on GOG, or at least visit the game page was promoting Extras for the game. So you might be wondering what the benefits are to buying it on Steam. The only advantage Steam has at the moment is Steam Achievements (if you want them). The advantage GOG has is, as it always is – no DRM. So while digging into my Steam directory, I discovered most of the GOG extras are included with your Steam version – it is just not explicitly told to you."

[Xristo]

I bought it directly from the developer's website. Got the DRM free version along with a Steam key.

[Perjoss]

Yeah it was quite a bit cheaper than the steam price and you get some nice digital extras too.

[StayStatic]

Same , seemed like the best deal imo , might have a go later, never played this sort of game before so it will be interesting to say the least.