The Preferences Panel lets you increase the sensitivity of the mouse. All it does is adjust the same value that the Mouse Pref Panel adjusts, but gives it a larger range. This has proven to be essential for external USB mice. I set mine to 3.0 with many external mice for happiness. Mouse Zoom homepage.
A simple suggestion: create a “Local” folder in /Applications to store all your non-bundled and/or downloaded software. This keeps things from getting too messy on your base OS/X install.
I use Xemacs a lot and I was having trouble with C-w C-u and other common emacs key bindings. I discovered there is a setting in the Keyboard Systems Preferences Panel that adversely affects the passing of keys to Aqua applications. Changing the Keyboard Access mode to Function Keys instead of Control Keys really made a big improvement.