Considering this now...but these require another separate client don't they? Not sure whether I'd rather just wait for a Steam key
Yes mate they require the twitch desktop app. I’ve never bought a game from them, but have 20+ free games that are decent, SuperHot being a favourite.
The app is one of the best I’ve used; fast, clean and simple. I like it.
If you go the trial Prime route just remember to cancel it; my Mrs forgot and ended up paying a years subscription.