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Oh, I'm not planning on relying on Steamworks exclusively, no. I was mostly thinking of some simpler integration, like Steam Achievements or similar. I already have my own in-game system implemented for these, but it'd be nice to give them out on places that support achievement-like features. I'm sure I can figure these out on my own, when the time comes.
MrFariator, unfortunately it is not as simple as that. Steamworks SDK will require authentication, stats and probably a few other features in order to get your achievements working. My recommendation is to roll out your own system and don't waste your time with Steam.
For a single player game, all of that can just be logically put into its own little corner in the codebase, only available in builds distributed via Steam. Other platforms can just have it excluded. It might not be a huge thing on my priorities list, but it's something I'll have to look into eventually either way because it's an expected feature.