In this video:

It's stated that all games are free to play, can somebody give some clarification as to what that actually means, I wasn't aware of this and won't be happy if we can't straight up sell games for a fixed price point.
If she means all games have a trial that's fair enough, but that's certainly not how it sounds in that video.
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Founder of ReachingPerfection.com
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If prices do go unlisted (which I can still say with confidence that I think is a good idea) I would have every intention of mentioning that my game would require a purchase for full access, maybe put it in the description, or as a disclaimer upon start up.
Out of curiosity where did you work? I think if all apps where listed without a price then you wouldn't necessarily be trapping people because they'd know upon download that mostly all games are just offering a taste.
I can't remember exactly where I read the info from, but I think it was when she was the keynote at some Android expo. Could've been the many Twitter posts too, I wish I could remember/prove it.
http://www.ouya.tv/game-developers-how-to-get-started-on-ouya-now/
Payments:
For unity, check this: http://answers.unity3d.com/questions/370761/google-play-store-multiple-files-for-large-apk.html
I assume OUYA will have something similar and that the unity guys are working on with OUYA on how unity can work with it
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If the OUYA store doesn't have any utility for showing prices (I'm hoping it does), you could just put the price in your game's store description, maybe even in the game title.
And yeah, Unity's Asset Bundle system allows you to download any non-code assets to load from, and you could get an account on one of the cloud services like Amazon S3 to store your asset bundles on. Of course, as Ayrik says, it's a Unity Pro feature, and also, my experience has been that assets stored in asset bundles tend to be slow to access after downloading, so make sure you take that into account, preloading them before you need them and stuff.
1) Users can download the demo version and grab the full game's asset bundle when they unlock it.
2) You can force people to download directly from your server where you can do a lot of analytics (ie: how many downloads, how many purchases total = how many pirated copies etc.).
3) You can do file chunking so users only download as much as they need. Player downloads the base APK that houses the main game logic. After that they launch the game and it determines which assets to download next. If they had a save game and they're 50% through your game, it would start downloading the assets needed to resume their game.
I would second this, but as someone else mentioned that may result in downloading a bunch of content that isn't necessary in the short term.
BUT, it does have the benefit of not having to download more content when purchasing the full version - the user gets instant access to the full game when they purchase.
There's pros and cons here.
I myself and developing a multiplayer game, and my game will restrict the player to singleplayer/practice mode until they purchase the full game (no content issues here)