Coupla things. Responding to your last point, that just goes right back to the idea expressed elsewhere of delaying access to the latest versions for non-donors, which has the problems I mentioned above, mainly the lack of bug fixes in older versions (which in severe cases can be a real issue).
As far as your feelings on the support model, I totally know what you mean, but it seems like all that only applies to other products and/or not already established products and/or open source systems where some other company can take the source and publish their own version of the product and sell support for it. None fo that really applies here, and it occurs to me that maybe we have a chance to do that model "right". In other words to take the stigma of that model and turn it on its head and make it actually work, for devs, for users, and for those providing "support". Essentially it's just a redirection of the payment *conceptually* but not necessarily practically.
It may not work for some philosophically, but essentially I see it this way: you justify providing the product for free/cheap (the alternative to your "just buy it" option above) by making the purchase price be for providing support. This doesn't mean you *don't* provide support for people who don't buy or donate, just that the buyers get "priority" if and when it comes to that. From experience I can say it seldom does, at least for the products I've dealt with. The purchase price though still goes to the author of the software in this concept, at least I think it should, partly because often the software author is the one providing the "support" (along with bug fixes, updates, custom features, etc. which can all be seen as support).
The problem I see immediately with it is the suggestion of payment for support, when support is now free and often provided by people other than the authors or you (mouser). Why are those people not getting paid? Well, again it's a bit of a conceptual zig-zag, but the idea is that the support purchase cost is really just a way to get people to pay a fair value for the software. Just as in your example where the value is somewhat imaginary (they could take the free/donate route). I'll grant though that in this it is perhaps a bit more disingenuous. Still maybe there's a way to get it to work. I don't think there's anything fundamentally wrong with getting people to pay for what they already get for free, that happens all the time and is essentially what this whole conversation is about. People pay for support all the time and don't necessarily get much *more* out of it than they might otherwise, e.g. sometimes the forums/community are the best support anyway.
So... more to think about perhaps.