Good parallel, tho hopefully it doesn't turn out the same...
There's an interesting dynamic, however, that I think many distros and others in the community considering this income option may not make enough allowance for.
At least here, I know I started on Mandrake (even buying the CDs) and was happy enough with it. Then I started running cooker with the idea of ultimately contributing, which of course meant downloading early versions well before they showed up in a proper release,and that too was great.
But then they came up with the Mandrake Club, and the relationship went sour for me, not because of the contribution, which I wanted and intended to make, but because of the inevitable "OK, I'm paying money for this now, is it worth that money to me?" reevaluation.
Basically, I started looking at where my money would go, and what they were offering for it? What were they offering? Primarily two things: (1) Snail-mail delivered ISOs for (to me on cooker) now long outdated versions that did me no good. (2) Access rights to proprietary servantware that for me was a net negative, since I had my fill of disregard of my rights on MS, and after a lot of personal time and energy spent learning and switching to Linux after a decade on MS, I simply wasn't interested in fastening that EULA leash around my neck and handing it to servantware masters yet again! Others might be fine with that and I was OK with Mandrake working with servantware for them, as long as I wasn't going to be contributing to it, but once they started asking me to contribute to THAT, it was an ENTIRELY different ballgame.
The club was also NOTICEABLY 32-bit x86 focused at a time when I was primarily interested in the new amd64 arch. They had amd64 available, but it was primarily server focused (with only server-targetted ISOs available for purchase and that not directly tied to club) and I was desktop/workstation. Unfortunately and probably as a result of the 64-bit server focus, amd64 cooker was based on x86-stable, so it was often more outdated than 32-bit stable, and the 64-bit ISOs available for purchase were stable amd64, even MORE outdated, IIRC up to six months behind what I'd actually be running which was already six months outdated on a lot of packages compared to x86 cooker, by the time I got delivery. Further, much of the price of the the amd64 ISO purchases would obviously go to shipping something so outdated on delivery it'd be about useless, so rather less of my money (as compared to the 32-bit focused club) would actually do anything for Mandrake.
So I spent some time trying to figure out how to contribute a similar amount in a way that would support reasonably current FREEDOMWARE amd64, and couldn't find any, at least with anything similar in terms of contributor-benefits. Nada. This company simply wasn't interested in providing product I was interested in, even tho I had the money in the bank and budgeted to Mandrake, and the check ready to write.
As I said, all this didn't really matter to me when I was simply downloading it for free and working on cooker, contributing what I could and planning to do more as I learned. But once money entered the picture, value-for-money entered the picture as well, and things looked MUCH less rosy, especially as I could see the company simply wasn't offering the products I was interested in.
It also sensitized me to issues I'd have otherwise overlooked, like the fact that they dropped quite behind (IIRC one 3.x version plus a 3.x.y) on kde around that time -- in 32-bit cooker, let /alone/ 64-bit, which due to being based on 32-bit stable, would be even FURTHER behind by the time 32-bit cooker actually caught up. As long as I wasn't planning on paying anything for it, only contributing to cooker basically as a hobby, I was unhappy with it, sure, but no big deal. Once they introduced the whole money aspect to the picture tho, even tho I hadn't actually paid (beyond my original off-the-shelf CDs purchased a couple years earlier by then) yet, I fully intended to, and that kde delay began to look a LOT worse!
So I ended up switching to Gentoo/amd64, with actually current kde, taking the amd64 system I had purchased with the intent of using as a tool for my Mandrake contributions with me. Turns out a community-based distro was a better match for me anyway, as was the build-time customizability of gentoo, tho the latter has little to do with the current topic.
Certainly in the Mandrake case, I expect this sort of effect wasn't really accounted for. They expected to get some level of money coming in, but didn't anticipate that introducing the whole money aspect would force user reevaluations and a higher demand for product tailored to specific interests such as mine, such that it would drive down satisfaction levels and ultimately drive off community contributors even if they could still continue with the free-of-cost product as they had been.
Ubuntu is of course a different product from a different company at a different time, so how parallel the situations are remains to be seen. They do seem to have a more centralized top-down decision structure and seem to target a user base that's not particularly interested in making that sort of decisions for themselves anyway, at least for the core ubuntu, so it may well be that they don't have this aspect of the community to drive off. But to the extent that they do, I hope that they considered the effect that asking for money contributions has on the willingness of the user to settle for a less-than-perfect match for their use-case, even for people who are already contributing in non-monetary ways but get the product free-of-cost, because the resulting drive-down of this aspect of community participation certainly didn't do Mandrake any good. But if there's little or no community of that type there anyway and/or they simply don't care about what is there, as may well be the case with Ubuntu as a commercial entity, then it could well be a net gain.