So I started with Gnome (Kharmic) and tried KDE 4 on a lark (Kubuntu Kharmic). Loved it, except that it was too buggy. Stuck with it through 4.5.2, and then went back to Gnome in Lucid. I liked Ubuntu's added touches and it seemed more solid, so I stuck with it until Natty. Hated everything about Unity, so I stuck in a FC15 Alpha LiveCD and after about 5 minutes decided it was so much better than Unity I installed it and have been running ever since.
I do Java development, system administration, E-mail, photos, backups, samba shares, PHP/Apache, and make heavy use of VMs. And for every single one of these tasks I find that my workflow has improved significantly. The notifications system, while immature, is a huge step forward over any other desktop environment I've used. With a few shell extensions and the gnome tweak tool I have everything I need: date and time top center, weather icon and details on the panel, places menu with shortcuts to the filesystem, etc.
I'll grant you, it's not perfect. The power options stink. I can't pin certain Java apps (NetBeans) or custom shell commands to the shortcut panel (e.g. VBoxManage --startvm "Foo"). It would be nice if there was first class support for samba configuration and other things. The system configuration menus are anemic and confusing, and a lot of stuff has to be configured via gsettings. But I only deal with those things very infrequently. For my everyday tasks everything is much better. (I make a lot of use of the expose feature and the search tools.)
Now FC15 as a distro, on the other hand, is a complete pain to deal with, and if Ubuntu provided decent support for Gnome 3 then I'd switch back in a heartbeat.