I am Ubuntu user since version 5.04 and it use to run on Gnome Desktop on 128 MB RAM comfortably. When Dapper Drake arrived I could install it but I had to add RAM to use it. I added 256 MB. Then the Laptop Display was broken and I converted the Laptop into Desktop by connecting an external monitor. This reduced available RAM to 312 MB.
I installed Gutsy and could use enhanced Desktop effects but it was very slow. I added KDE 4 also just to see what is coming but it was slow. For daily tasks I added Fluxbox. Then I saw LXDE thread and added LXDE. Since then I was using LXDE and liked it very much.
For Hardy Heron I decided to do Cli install and add Window Managers one by one. Initially I added openbox and fbpanel. Then I tried to install lxde meta package but it failed to install due to unmet dependencies. I checked the dependencies and could not find 3 packages in Ubuntu repositories. I downloaded these packages from Debian and installed through dpkg. Finally I could install LXDE Desktop.
Initially, I did not install any Login Manager and was using startx command after console login.
Today I discovered slim login manager and installed it. On Login Screen I could select the session by pressing F1 key. The first option was XFCE which I had not installed. After pressing F1 again the second option was openbox and I could login to openbox. Third option was IceWM, so I installed IceWM and could login to IceWM session.
I searched for "slim" files and got /etc/slim.conf file. In the section "Available sessions" I changed "xfce4-session" to "lxsession" which also became the default session.
Now I could login to LXDE Desktop. Then I thought that I should add all light weight WMs to the sessions and downloaded Fluxbox and JWM and replaced "wmaker" and "blackbox" with "jwm" and "fluxbox".
I really like these "Slim Ubuntu Desktops" and slim login manager.