Does this required Unity Pro?
No; tri-planar shaders do not require Unity Pro however some shaders may require Shader Model 3 or in the case of the World group of shaders you will need to use DirectX all of the above settings are available in Unity Indie aka free however mobile devices may have there own limitations typically model 2. While many of the simpler shaders will run under 2 you will find that the more complex shaders render purple, black or fallback to a simpler shader.
I need to tile or offset the texture how do I do it?
Heathen's Tri-Planar shaders respect Unity's built in texture tiling and offset values; with the exception of World shaders which ignore the offset but do respect tiling settings. You can edit this value on the material its self.
My texture is over-bright or covered in white...
This is most likely a specular or "Shininess" value that's set to high; in particular World group shaders are rather sensitive with this value. You can further adjust this bu setting the Specular Color to a darker version of what your currently using.
How do I use a Parallax tri-planar?
Heathen's Tri-planar Parallax uses the same methods as Unity's stock Parallax shaders. While the Parallax height map is traditionally a grey scale this is a matter of file size; its actually the Alpha of the texture that determines the height; if your image has a flat alpha value then you wont likely notice any difference.
All my textures are offset ... why?
Object based projections are made from center or origin this may appear as if the texture is offset by 0.5 if your where to put the material on the stock cube or sphear. If you need to correct simply set the offset to 0.5 on all textures for the shader.
The texture seems to scale ... why?
Object based projections find the size of 1 full UV based on the object scale; if the object is scaled evenly across all 3 axis then the texture may appear to be scaled by the same multiple. You can use the tiling values of the material to account for this such as placing blocks of increasing size next to each other where each block's scale is a multiple of the previous; in this case you would set the tiling to be a quotient of the previous.
Is there a reason I would use World as opposed to Tops?
Yes; World calculates Top and Bottom slightly differently than does Tops shaders. With Tops which are object scoped shaders we plot "top" and "bottom" by there relationship with origin where World has no origin; "top" and "bottom" are plotted by the direction the face is facing. If your wondering why we don't do the same for Top its because it would slow the shader down a lot if we plotted the direction the face was facing with regard to the object as this would require us to calculate the objects rotation before finding the face orientation.
You could adjust the Tops grouping of shaders to do this if you like; take a look at World and how it calculates UVs in particular Top and Bottom for hints.
World Shaders render black for me...
You need to set the Player settings to use DirectX in order to use World group shaders; you see black because the shader has fallen back but there is no MainTex defined this is intended so the broken shader sticks out like a sour thumb in your testing :)
If you want the shader to fall back to a shader that can render you could simply set the Fallback to call one of the Tops shaders as they use the same texture names as World but are object scoped textures many of which can render under Shader Model 2 if need be.