You've probably had 20 other people tell you about this; but switching to a tiled window manager will remove that whole 'careful placement of windows' thing from your life in a very positive way.
- No simple way to keep a small IM status window open in the corner of a workspace
- Limited support for resolution-dependent windows, such as videos, games or remote desktops
- No notification bar for status apps to utilize, such as pidgin or network-manager
- No integration with modern desktop environment features or tools, such as media keys for rhythmbox, launchers like gnome-do, network-manager, automatic disk mounting, screen lock, etc
Gnome and compiz have solved a lot of problems that actually make a Linux desktop usable in modern contexts.
Apologies for the evangelism. :)