Hi, Daniel
When you talk about "desktop users", I think you really mean "novice consumers". Is that a fair assessment? In my experience, Debian can work just fine on the desktop in some situations, just not for novice home users. (think, e.g., about desktops for office workers)
We have had 50 Debian desktop installations in our organisation, and the users have had some legitimate needs, and were not happy with some usability shortages or bugs in some basic software found in Debian Sarge (OpenOffice.org, Firefox, Thunderbird, and so on). Since we use these applications massively, and have to communicate with outside word, and those installations have been pilot project to whole organisation's migration to Linux, it has been important for us to make the work environment as flawless as possible.
The issues have beed reported upstream and fixed, however the only way to get the fixes to end user was to abandon distributional versions completely and install generic upstream packages.
Thus, I assume that not only novice consumers have the need for improving desktop software and bugs seen fixed.
However, Debian dosen't officially support and embrace any way to do this. Watching for new version, You're on Your own.
Why would you want this? In a setting where you have people doing productive work using a piece of software, unnecessary changes to the software are *worse* in the short term than a fixed and unchangable set of bugs: not only are changes likely to break the software, but they may require users to retrain or disrupt the processes of your organization. This is true even if the new software is an unqualified improvement (either in terms of bug count or usability) over the old software; look at the backlash over the new Ribbon interface in Microsoft office, for instance.
Yes, if software works well, then changes are not wellcome. That's why I suggest the desktop softwares upgrades to be "non-mandatory", however officially supported.
Peter