I don't think the OGL was as successful (for either WotC or 3pp) as it could/should have been. Some of that can be attributed to malice, greed, or selfishness. But I think most of it can be attributed to confusion, uncertainty, inexperience, and not-invented-here syndrome.
It was a great experiment, to take something that wasn't (and still isn't) fully developed in the software world and adapt it to a publishing model. The proponents of the OGL deserve extraordinary credit for vision and determination, and everyone who published OGL material gets a pat on the back for being a part of it. It's unfortunate that we likely won't see a second generation of it, because such radical departures from the norm are rarely perfect from the get go. Another generation of refinement, and a generation of designers and publishers who grew up in a post-OGL world, would have made things even better, I think.
Even if you never bought anything but WotC books, you benefitted from the OGL, just like you benefitted from any other game that's been published that you may never even have heard of. None of the work done for 3e or 4e was done in a vacuum.
The GSL is a result of corporate need, nothing else. WotC wants the whole pie, and they want to decide who gets the crumbs and under what circumstances. Perfectly within their rights, of course. As a capitalist, I can appreciate that.
But I hope people understand how anti-customer this is. More than most any other product, RPGs require great effort by the customer to be useful, and the reward is as much, if not more so, a result of that effort than it is of the product itself. The more material that's out there -- good, bad, mediocre -- the better off the hobbyist is, because you never know where the diamond in the rough is, or where you'll *yoink* that next cool idea for your campaign. The magic of role-playing games comes from the DMs and the players first and foremost, but none of us operate in a vacuum either, and the more we're limited to a single publishers vision of what gaming should be, the worse off we are.