I have this mesh with a full size texture added on one side. When I look at the texture at a shallow angle, texture further from view point gets extremely blurry, almost like I have some kind of depth of field filter on
How do I get my texture 100% sharp?
Those are caused by Mipmaps, it is an optimization technique to improve performance and rendering speed of the viewport. It works by automatically creating several copies of used image textures at different resolutions or sizes in GPU memory to speed up rendering.
The blurring is an unintentional side effect of the lower resolution used at larger distances or grazing angles. It is harmless and affects the viewport only, it will not affect your final render image.
If you don't like it you can deactivate them in User Preferences > System > OpenGL > Mipmaps or control GPU generation.
The reason Mipmaps are around in the first place is because sometimes you want the blurred image since it represents "the average" pixel value rather than the "exact pixel at this one point" -- noisy textures will look grainy or flicker in motion (temporal aliasing).
If you don't have issues with grain or flicker, you can turn off Mipmapping in the UserPreferences > System pane (see Duarte's Answer) But you could also try increasing the Anisotropic Filtering value (which basically means that the texture will be averaged more in the short direction than the long direction). This is a more expensive calculation but will achieve the de-graining of mipmapping without the blurriness.
