With all due respect, which isn't much the original poster reads as entitled as entitled can get. They have two posts, the first post is complaining about being able to upload a file, help was offered they have as yet not responded but it goes along the lines of I have an issue, your code sucks, its embarrassing, your programmer is at fault etc etc and not a drop of information on the issue itself.
They follow that up with this idiotic post!!! which goes on the attack yet again!!! and yet again provides very little details on what issues they have run into!!!
I understand people have issues and that sometimes things do not always go to plan, but if you are running a mission critical application, run a staging server/dev environment or similar to test before you update have at least 1 nighty backup, stored for 7 days and maybe a monthly one.
If all of this isn't something you plan to do or you are having problems, hop onto these forums where people give up free time to help you with your issues - remember the LEAST you can do is explain the problem you are encountering and try cope with your frustrations in another manner, nobody wants to help someone that comes in abusing them.
In terms of frustrations of the platform possibly breaking backwards compatibility, this happens infrequently and its frustrating when it does happen between minor versions but in most cases its likely a bug, developers are not out to sabotage the very small pool of extension developers they have.
If you do run into an issue after an update this is when you do the thing above and drop into these forums, provide the relevant information so someone can provide there free time to help you fix whatever issues you have and maybe, just maybe advance the platform.
This isn't customer support, get a grip.
in terms of what mission critical extensions are, that'd be the ones shipped with core, everyone has an opinion on what should and should not be included within the core release. FOF has been a godsend for helping people (like myself) by picking up abandoned extensions and ensuring they are functional going forward but this has a breaking point.
If you REALLY need an extension (i.e you are using words like mission critical) then slap a bounty on it. Doesn't need to be a big bounty, couple of $ to entice others to drop a couple of $. I've seen plenty of extensions with promise already picked up and supported with and without bounties this is not obviously myself saying if you want an extension supported you should pay for it, I'm saying if you value an extension to the point your community needs it to function then perhaps its in your own best interests to speed up a new developer picking up an existing extension.