I represent the newer school of D&D-players, having gotten my start sometime after the release of D&D 3.5. I also live in a part of the world where role-playing games in general and D&D in particular is a very rare hobby, and only a very few people play it, with the nearest hobby store carrying RPGs being a seven-hours drive from where I live. A friend's older brother introduced my group of friends to the game, though, and most of us got pretty heavily invested in it - within a couple of years, I had hundreds of dollars worth of D&D books lining my shelves, much more than I was ever able to find use for playing the actual game itself (and yet, that didn't stop me from buying more, more, more). As the setting we used when we first started, the Forgotten Realms became my setting of choice, and there's only a very few books released for it under 3.5 that I didn't wind up purchasing (and a good deal of 3.0 books was picked up as well, because they helped me learn more of the lore of the world, of the flavor, which I'd fallen in love with). I had my experiments with homebrewed settings and purchased a few Eberron-books as well (I like the setting, I like the feel of it, but when I'm the only person in my group who knows the first thing about it, and has any reason to want to play it over the FR, it didn't really get much use), but in the end I always came back to Forgotten Realms. I even started buying the FR novels, as did a couple others in my group, and though I've heard a lot of criticism about them in the years since, I thoroughly enjoyed the books and the setting, and I would have gladly gone on supporting the setting (and, therefore, the game) for years to come in the future as well.
Then, 4E came around. Like a lot of people at the time, I was skeptical, I didn't want my massive 'library' of books to become obsolete. At the time, I was part of a play-by-post community devoted to the Forgotten Realms, with each DM taking on his own region (so one person would run Waterdeep-campaigns, another would run his in Icewind Dale, and so on), one that had been around since the days of 3.0 and already made the change to 3.5. Most players and DMs were heavily opposed to converting to 4E, being happy with the way the game ran, but personally, I wanted to give it a try at least, to find out for myself if this new edition would lure me in or leave me cold. When the game came out, I'd moved to another town - the one town in the region to have a FLGS - and so I stopped by there, had a look at the core rulebooks... and I was pleasantly surprised. I liked what I saw, at least in theory, and I wound up purchasing the core set, and later the PHB2 and DMG2 as well. It wasn't the same game that I'd been taught, but I could tell I could learn to enjoy this one as well. Then, something happened that stole every ounce of sympathy I had for WotC, who's products I had by then spent most of my disposable income on for several years. I'm talking about, of course, the Spellplague.
As someone who cared more for his setting than the game system, the changes WotC did with Forgotten Realms in 4E felt like a betrayal. To this day, when I look at all the changes they made, I can't point out a single one that I prefer to the way things had been before. A Dragonborn empire sprouting up, just because they had been included in the Player's Handbook, when there was no justification for them in the lore of the Forgotten Realms? Dozens of deities being killed off to 'streamline' the pantheon, some of them among my favorite deities in the setting? And a century-long leap ahead in the timeline? Ugh. It felt like someone had tried to make it a Forgotten Realms designed for people who *didn't* like the Forgotten Realms in the first place, instead of updating the setting for those of us who loved it, had spent hundreds and hundreds of dollars buying sourcebooks and novels and video games based on it. Selling me more Forgotten Realms should have been the easiest thing in the world, but instead they chose to go after another market entirely. It frustrated me to no end, and though I know I could have used the old setting with the new rules, I was displeased by WotC enough at this point to want nothing to do with their products - I had a ton of 3.5 books, more than enough to keep playing in 'my' Realms for as long as I wanted to, with no need for new updates and supplements.
A couple of years later, I first heard about Pathfinder, and though I remained skeptical at that point, I realized that the changes in the system were far less intrusive, and the changes they did make were ones I happened to agree with, in some cases changes that I'd wanted to see happen for a while. I went into it slow - $10 for the PDF of the Core Rulebook seemed a fair entry point, and the more I saw, the more I liked. I can easily convert any 3.0/3.5 statblock from my Forgotten Realms sourcebooks to Pathfinder, making it much easier for me to convert to it than 4E, and as I started learning more about the Pathfinder campaign setting, Golarion, I came to enjoy that as well. Today, I'll gladly play either 3.5 or Pathfinder (with Pathfinder a slight favorite if I got to choose), and I have two settings to play them in, and chances are good WotC has seen it's last penny of my dollars - well, at least for their RPG products, some of their new board games look interesting, and dungeon tiles and miniatures could always come in handy. . .