If you miss simple and fast. If XFCE isn't your bag. If you just want a simple UI without the massive over head of KDE or GNOME. Give LXDE Desktop for Ubuntu a go.

sudo apt-get install lubuntu-desktop

I'm currently enjoying it because it makes my P4 seem snappier.

Love the:
PCManFM 0.9.7 (File manager)
LXTerminal 0.1.9 (Terminal)
Sylpheed version 3.1.0beta2 (Mail client)
abiword 2.8.6 (Word Processor)
Gnumeric Spreadsheet 1.10.8 (MS Excel Replacement)

Everything seems to launch very snappy.

You don't loose the normal task bar clients such as the network manager client (nm-applet).

I'm not quite ready to give up the start ==> programs ==> application paradigm just yet. While I like the new Unity 2D Desktop on Ubuntu it still has a lot of bugs to be squashed before it can be considered ready for the big time.

So for now I'm giving the Lightweight X11 Desktop Environment (LXDE) a go.