I love the Challenges! I think they're a great motivational tool and organic way to form mini-communities. But, they feel kinda distant from my normal DM experience. The only way to see results is to go back to each Challenge. And I often forget I've joined, so I don't go back until way too late.

I'd love to see Challenges integrated into the DM experience a little more. for example, the ability to target a workout to a particular Challenge (that way my Hill Challenge miles won't be completely flat ;-). also, a reminder on my profile or home feed that I'm currently in X Challenges. or, a message on my home feed when I complete a Challenge.

these are just my thoughts; please feel free to post your own ideas about how to make better use of the Challenges!