I"m not so sure that some of the "complaints" are even from people who use GS/G3. There were comments like "There should be a theme manager". Well before this was Gnome-Tweak, but the latest version includes Tweak as apart of GS itself. You can install plugins and change themes using this tool.
Some of the suggestions are valid, but a lot of them seem to be KDE users wanting GS3/GS to be KDE.
Hmm. Every time I think about trying Ubuntu or Gnome, I find alot of UI complaints for both Unity and Gnome. I don't think that there is alot of "noise" here as one poster put it- the users are clearly unhappy. If you don't care about your users, you're basically just writing a piece of software that noone will use which is completely useless.
I use Arch/KDE4, and before that I was openSuSE/KDE3-KDE4. When the KDE4 switch started happening alot of people were unhappy but the users understood where the KDE team was going and had praise accompanying many of the complaints. Here is it solid negative. Gnome 3 reminds me of the Amarok 1.4-2.x switch, to this day I refuse to use Amarok for its bloated, too simple and non-functional UI and the Phonon nightmare. I ended up writing my own media player that uses PHP, MySQL and AJAX/Flash instead, and that solution is much more powerful.