Well, somebody gave me several gallon kits of D76, so I am actually moving TO it from Xtol and Edwal 12 until I have used them up.
There is no developer that is as interesting as a good picture, and there are zero pictures that I photographed where I had wished I had used a different developer.
Here's the deal: It's nice to use the same developer over and over again, because it's reliable, consistent, and we learn EXACTLY what to expect that way. That is very good for darkroom exercises, because it leads to less paper waste and less frustration. That is definitely so.
That doesn't mean that other developers aren't interesting too, just from either an academic stand point, or even something we're just curious about. While I love replenished Xtol, D76 that cost me no money at all must be just as good. I doubt it will make enough difference for anybody to truly notice, after I develop the film to the same contrast.
Among other gifts, I also have a gallon kit of Microdol-X, and a bottle of Sprint film developer. The Sprint is what I'm currently using, and it's a fine developer too. The prints look very nice.
I find it more valuable to learn exactly how to use a particular material, and find that there is infinitely more strength in that than any one product in itself. D76 / ID11 is great stuff. So is Xtol, Rodinal, Pyrocat, HC-110, Microphen, Microdol-X, Ilfosol, Moersch, Foma, Adox, Tetenal, Edwal, Formulary, etc ad nauseum. They are all great products - in the right hands.
It's all about making nice negatives that helps us make nice prints.