HapticSimian: Fair enough. Danny Sullivan made a similar point: just because you're running an old version of Android doesn't mean your mobile experience is completely crippled. But I do think there are lots of legitimate reasons to want to be on ICS or JB. The biggest one in my view would probably be the ability run Chrome - the difference between that and the stock GB browser is like night and day. Not to mention the improved UI, improved system apps across the board, etc.
And yes, this is just "capitalism in action". But if we're going to vote with our wallets, we might as well communicate our reasons to these companies so they at least know what they're doing wrong. (On that note, if any HTC representatives reading this forum: my first two Android phones were both HTCs. I have since switched to a Galaxy Nexus. The main reason I ditched HTC was because I gave up hope of ever receiving updates.)
Another point in Android's favour is that at least when Android phones do get updated, they get all the features. For example, all Android phones with 2.0+ can do turn-by-turn navigation, and all phones that get Jelly Bean will be able to use the new voice actions. Thankfully Google does not engage in Apple's scummy tactics of forced obsolescence and holding back features like Siri and navigation from older handsets that could easily handle them on a technical level.
However, my point has never been that iOS is better than Android. (If I believed that, I would use an iPhone instead of an Android phone.) But clearly Apple does do a much better job of supporting old handsets than any of the Android OEMs, and I would like to the Android OEMs improve in this area. If they could do a better job of pushing out updates, that would be good for consumers, good for developers, good for the Android ecosystem as a whole, and it would also be good for the OEMs own brand loyalty in the long run. If the OEMs drag their feet on this, then we as consumers can and should criticise them for it.
I'm glad that you've had good experiences with MIUI, and that you've found it to be a reliable ROM. But to be honest, that sort-of proves my point. If a bunch of hobbyist Chinese developers who aren't even getting paid for their services can make ICS run reliably on the Desire HD, then why the hell can't HTC's own developers do the same thing, and then push out OTA an update for all those people who don't have the technical knowledge to flash custom ROMs? It is outrageous and pathetic that these companies can't support their own hardware as well as amateurs who do it for free.