I have downloaded apps - both free (Netflix, Crackle, HBO, etc...) as well as paid for apps - Geometry Wars 3 just this weekend.
I have an XBox One also - It's just much quicker / easier to just flip over to Apple TV and start a game then to go through the whole process of booting the XBox, putting in a game, etc... I'm not a hardcore gamer by any means but I play when I need a break.
Missing from Apple TV still are Pandora / Spotify / others... I'd like to see some party games - trivia, card, etc...
It's definitely difficult to find new apps - the on screen keyboard is garbage and really needs to be worked out. Just give us a nice vertical scrolling list with categories on the left.
IMO - it's still very new and developers are trying new stuff - see what works / what doesn't. The Netflix app is an example of this - the new interface is absolute garbage. I've actually fired up my XBox to use Netflix on that instead of Apple TV now...