If you're into indie games, chances are you've heard of Waking Mars by now. If you haven't - check it out, this is one seriously awesome puzzle / platformer mashup with an epic story and amazing soundtrack. It actually just hit the Play Store, too, after being available on Android exclusively through the Humble Bundle that went live last week (still up now).
So, why buy it for $5 through the Play Store instead of the pay-what-you-want Humble Bundle? Well, I can't really think of a good reason aside from updates, or simply to support the developer (that's always a good reason). I guess it'd be easier to install across multiple devices, too.
Anyway, if you do think of a good reason, hit up the Play Store and grab it.