Layers are useful but don't get me wrong if i can keep the layer count down I will. Take for example the watched spectacle icon here that was about 8-10 layers (can't recall) but I got that down to 3 layers so I do definitely avoid over using layers when i don't have to. It makes for easier management when you have to re-visit the PSD and with PSDs you can have many sets that can mount up times the amount of layers in that set which can be a nightmare if it's not managed correctly. Suffice to say, and I hold my hands up I am a downright messy when it comes to layers not naming them and sometimes over-using them but i always end up coming back to the PSDs and tidying it up.
I have no issues with other programs. I have seen some great creations especial icons created in GIMP which are really outstanding designs. I like to think that the software used is only as good as the person/designer using it. If a designer is comfortable in let's say for example GIMP then that is definitely the better program to use, if it's PSP then that is the better program, for that person/designer. I never really got into the whole debate Photoshop vs Gimp vs PSP vs inkscape because each program has it's benefits and drawbacks and each person has their own preference which they are comfortable in using so it's really down to - what works best for you.
jeez I'm rambling.
*submits*