Posted December 23, 2014

In the longer term, I'll probably want to ask the guy who runs ITAD to extend the API my import userscript depends on so that it can replicate the "warn of dropped entries" functionality already present in the Steam and Desura API sync.

One added benefit of backing your shelf and wishlist on MaGog is that it allows you to then compose queries involving both your private information and the public GOG data (e.g. which games on my wishlist are currently on sale with at least 50% discount and costing no more than $7; e.g. find me an RPG I own published in the 90s with a GOG rating of at least 4.7, etc.).
As for functionality, I think I'll stick with ITAD. Aside from filtering by attributes like genre, publishing date, and rating, ITAD already lets me do that across multiple sites. (And, unlike MaGog, ITAD is aware that I own over 10% of GOG's collection via Humble Bundle Inc.)