I'm the total opposite of Melissa, lol.

I don't have enough control with a mouse and feel like I have much more natural control with the tablet, especially because of the pressure sensitivity. It's just more natural for me and probably has something to do with being used to drawing and painting. I use the tablet for photoshop, illustrator, even surfing the web if I'm too lazy to put the pen down and grab my trackball. lol
Almost 15 years ago, not long before trying my first tablet, I made the switch from using a mouse to using the Kensington Turbo Mouse trackball. I found that gave me much better control in photoshop than a mouse did, especially since you never ran out of mouse pads space. It made drawing paths and tracing things much much easier.