OpenGL ES 1.0 on Android: blurry 2D images

Hi!
I am trying to port my game to the Ouya and in the process learning OpenGL ES (on Android). I got a 2D tile-based game. My game graphics appear blurry, both when drawn in 1080p and 720p (where 1080p is the version thats not being scaled, but looks the worst). When moving the level, horizontal and vertical lines start to flicker.

I don’t understand this, because I am drawing the tiles onto the screen unscaled, shouldnt they be drawn pixel-perfect?. I googled a lot and tried the following:

[ul]
[li]All Tilesheets and even individual tile sizes are powers of two already (so f.ex. a 256x256-file containing lots of 16x16-tiles)[/li][li]Texture scaling with both GL_LINEAR and GL_NEAREST look the same. I am not using MipMaps.[/li][li]All sorts of different screen sizes, not only 1080p and 720p[/li][li]Allowing and permitting coordinates of tiles that are not integers (only integer coordinates would allow for pixel-perfect drawing, right?)[/li][/ul]

I am using orthogonal projection of course, as this is a 2D game. All tilesheets are *.png files and are not being scaled (at least not directly by me, what OpenGL does in the background I don’t know).

I started with a version of the game using basic Android Bitmap copy-routines (not using OpenGL at all), which of course was very slow, but at least the graphics were perfect. So this is not due to the Ouya or my TV.

Does anyone have an idea what I might be missing? Thank you