first of all: welcome to the forums!!
I've edited photos using digitizers and mouse, but never directly on a screen such as your tablet or a touch-sensitive monitor, but I went back to using a mouse as I was never really thrilled about the pen. For extended sessions - not unlike handwriting - I felt it fatigued my fingers and hand.
The merits of these gadgets depend a lot on your work flow, I think. For the most part, I don't hand draw, but use the selection tools (lasso and "magic wand"). Everything else I do on my PC is with the mouse as well. FOr more free hand type stuff, I guess would be nice for someone who perhaps already paint or for someone who doesn't get tired fingers from using pens.
In my case, I don't feel that the extra price for this is warranted - I'd rather spend the difference on larger monitor, precision mouse, better processor, GPU and whatnot. But that's just me.