The reason I started running Dungeons and Dragons in the first place was that with the release of 3.0, the rules didn't suck any more and I'd have access to all that pre-made content. The rules weren't (and still aren't) my favorite, but they did have their good bits and the appeal of being able to grab a module off the shelf (or more likely a scenario out of Dungeon) and just run with it, combined with the available player pool at the time, made it the best choice for the group.
Thing is, D&D has a surprisingly large amount of baggage tied up into it. Not in the "conflict resolution" mechanics so much, but in things like the existing spell lists, class types and assumptions, etc. The main thing that D&D is good for, really, is running a D&D campaign. If you want to do something more sword-and-sorceryish, or port the game to an existing setting (Middle Earth, for instance), you have to do a lot of tweaking -- including tweaking of E-Tools if you intend to keep using it.
And frankly, once you get past 3rd level or so, you really need E-Tools or something to handle all the fiddly pieces of character creation. There are so many miscellaneous modifiers, weird synergies, and exceptions to everything, that it's just too much to keep track of. Just look at how you determine the stats of a melee weapon, for instance:
Base attack bonus + weapon bonus + Str bonus (unless using Weapon Finesse, in which case it's Dex bonus) - two-weapon penalties (if applicable), -5 for each iteration after the first if you have iterative attacks, - penalties for flurry or other rapid-strike type abilities, + any buffs that apply (such as bless, morale, circumstance bonus, flanking, charging), - any debuffs that apply (bane, nausea, lack of proficiency)
Main-hand: dice + Str bonus (nice and simple)
Two-handed: dice + 1.5 x Str bonus (and a 1-for-2 trade if Power-Attacking)
Off-hand: dice + 1/2 x Str bonus
On a critical hit: x2 or x3 damage, depending on the weapon type, with bonus dice for magic damage (e.g., flaming sword) doubled, but bonus dice for "precision damage" (e.g., Sneak Attack, Skirmish) only added once.
Crunchy, crunchy, very crunchy. Not that it's a bad thing, I like lots of tactical fiddliness myself, but it's a lot to keep track of. On paper, it's a big PITA.
Anyway, the point is, that D&D as written doesn't lend itself to a lot of customization, because it's all so intricate that you need some kind of tool to keep track of all this stuff, and customizing the game also means customizing the tool.
This can be gotten around by using a game system that's built with the intention of being customized -- The HERO System is my personal favorite -- but that has the problem that such games usually aren't exactly swimming in support materials. D&D had a module-a-month in the form of Dungeon magazine (and will continue to do so with Paizo's Pathfinder series), and even if you didn't like that, there were tons of third-party modules (e.g., the Dungeon Crawl Classics line) that you could also use pretty much straight off the shelf. You want to run a Fantasy Hero game, you have to stat up everything yourself. Fortunately, the rules already exist and cover exactly what you want to do, you just have to apply them. Unfortunately, you also have to teach your players how to apply them, and if they're not the Mad Game Tinkerer that you are, it can be quite a struggle.
As D&D moves forward, without the support of new products in E-Tools, my game mechanics "toolset" is pretty much frozen. Any books that come out with cool new mechanics or nifty classes are going to be useless to me unless I can easily hackify them into E-Tools as it currently exists. This has already caused me to choose against using the Duskblade class (from PHB II) for an NPC, because it never made it into E-Tools.
On the other hand, any products I'm likely to use in the future are all OGL and made from the core ruleset anyway. Paizo's Pathfinder and Gamemastery lines are all OGL, as are the Dungeon Crawl Classics. The only thing that got me to use WotC-specific "closed content" rules was their appearance in Dungeon magazine. So it may be that all WotC has really done, in my case, is to convince me to stop buying their products -- because what good are they to me now?
All of these thoughts and more have been running through my mind on the topic of gaming lately, and what repercussions this was all likely to have on my game. I've got plenty of 3.5 material and a perfectly viable copy of E-Tools that will easily take my current campaign to its conclusion -- which is not likely to be any time soon anyway. In the meantime, I'll be a lot more open now to other options for one-shots or off-games. Maybe there's something else out there that will suit us all better. We'll see!