In our group, there are 5 people.  2 of us GM frequently (including me); and 1 has GMed in the past.  The other 2 are players only.  We have had plenty of d20 games, including D&D & derivatives; but I still say it is hard to find a d20 GM.  More precisely, it is hard to find a d20 D&D DM.  3.0 is the best edition in my opinion, but the shine is off the penny for me.  I was the biggest proponent of d20 in our group (or groups--past & present).  I would still run some d20 games, but D&D is just too hard.  And I ran a core game for the most part.  Most d20 OGL games approach D&D levels of difficulty, but none really equal or exceed it; and they all just confuse the game.  It's just not worth it.  It's too much work for not enough play, even with pre-printed adventures.  Maybe a succession of low-level games or heavy modification of the rules would work, but I haven't hit upon a way to do it yet.