It would totally depend on what products were made with it.
For me, the awesomeness of the OGL was/is best reflected in the products by Necromancer Games and Frog God Games. If the GSL had prevented those products from happening, then I would not have lauded the GSL as much as I do the OGL. Since Necro shied away from the GSL, my guess is that they would not have made the products they did, and the gaming world today would suck.
If the product volume produced under the GSL for 4E was the same for 3.x, then a lot fewer people would likely care about the license *unless* the GSL was used by people (fans) to just put their own stuff on the web (not charging for it) without being sued.
While I grok what you're saying, I'll still point out that you would have never known that those products weren't produced... so how could you have made a decision to withhold your appreciation for the license?
As Morrus has noted... the GSL ain't that bad, I think this is especially true if you don't have physical product. For a PDF publisher it seems to work pretty well. If you have physical product, then you better have a plan for your inventory (Yikes!).
I have an alternative theory as to why the GSL isn't as popular as it could be. I think the DDI sucked a lot of the air out of the space where 3PP might exist. Every 4e group I've played with uses the DDI tools to some extent, and because it included the magazines, the character builder (and later the monster builder, etc) there really wasn't much space left for other publishers... with, or without, the OGL.
Sure, you could make content for 4e (and some did), but if you added new classes, powers, feats, etc... you were basically asking your audience to stop using the WotC tools. So anyone that did make a sale via the GSL was likely to end up with some frustrated folks on the other end. WotC was obviously not able to take on the technical requirements to make a character builder that allowed user created or 3PP content. Heck, they were only just able to keep up with their own changes and updates. The result is that those brave folks that did sign up for the GSL may have sold some product, but probably not as much as they could have if they had access to the DDI tools or if those tools didn't actually exist.
I should note that, people did eventually backwards engineer how to update the content in the original character builder... which was stupidly built for Windows systems only. And then the replacement was stupidly built with Silverlight (though this made it at least workable on MacOS). At any rate, I honestly think that the DDI tools were a subtle, but difficult to overcome, barrier to getting more 3PP content for 4e. Even those folks that created their own homebrew classes, feats, powers, etc would have been frustrated by the fact that they couldn't use them with DDI.
Anyway... just some food for thought. I could be completely off base here.