Well, for myself, I tend to use d20M WITH Grim Tales, for alot of things.
For instance, GT's equipment chapter gives great rules for BUILDING equipment (as a Game Master) but no equipment list like you have in d20M.
GT's Wealth system breakdowns skip a few gradiations, but at the same time adds in some extra rules on item rarity and town sizes that makes it great for fantasy games.
GT lets you do fantasy by breaking down alot of the D&D archetypal abilities and putting them into the form of talents, which I like alot ... but then Ben's personal biases leak through a little in places and a few of the abilities he wasn't fond of are sort of odd to get (like having to go Dedicated/Charismatic 3/3 to get Wild Empathy).
You can build a Paladin in GT, for instance, as easily as you can build a gunslinger. I like that.
For some reason, we didn't really like the GT skill system very much (EDIT: As far as the aquisition of class skills through backgrounds go, and for us, the number). Though Wulf's said he doesn't really use the backgrounds either. We stuck to it per-the-book and everybody felt really really limited skills-wise. I ended up giving away some free Class Skill choices at 4th and 8th level for folks so they could expand themselves a little more. At the same time, I REALLY like the GT skill system ... choosing your own skills, everybody getting a Profession ... but everybody getting a Craft seemed odd for a modern game, etc.
--fje