Is unity3d good for making 2d games or apps?

I have a few questions relating to 2d in Unity3d hoping someone can clarify.

If one wanted to make a 2d game, would it be better to go pure 2d or make it in 3d and have it appear as if it’s 2d? What if one wanted to use characters made from hand drawn HD 2d sprites? Should these be attached to a 3d model or would it be better to go without 3d?

I know some APIs have a problem with off axis pixel coordinates causing 2d images to blur when preforming float calculations, which means the API is not recommended for 2d. Not sure if that’s a problem in Unity.

Should the GUI be used for all 2d games? or is the GUI just used for menus?

I just used unity to create a 2d game without any problems.
You can easily use unity to create 2d games, and enjoy some of the benefits of 3d (for example having many layers of 2d objects).

There are also some nice 2d tutorials and also 2d tools that make it easier to create 2d games with unity.

Take a look at the following links:

Nice unity 2d video tutorial from start to end: Hathzynx - YouTube

Asset store page for 2d tools (includes one that is free): Unity Asset Store - The Best Assets for Game Making

Another nice 2d tutorial, not video:
http://www.rocket5studios.com/tutorials/make-a-2d-game-in-unity3d-using-only-free-tools-part-1/