I can't stand how the cursor for the brush tool is an actual brush in Illustrator. It makes it really difficult to see where I am going with the brush. Is there a way to change it so that the cursor is a circle that shows you exactly where you're about to brush?
Yes, open Edit → Preferences → General (Ctrl+K)
(This applies for all of the tools.)
Also, to quickly toggle it on/off just hit Caps Lock