The purpose of UVs is so you can create a 2D texture for 3D space, right?
So if your method of creating the texture in 2D space (e.g. PS) results in a non-distorted render, you should be fine.
Another way of looking at this is to paint a straight line in your texture space. If the line is also straight on your model, you're good. This doesn't necessarily mean that the UVs themselves are in a gridlike pattern.