It's been a couple of years since I did anything with imaging, but sysprep comes in handy for several reasons.. Like it was mentioned before, we can customize the default profile so the user gets the corporate logo'd background and UI tweaks we want right out of the gate, the initial boot process after sysprep will automatically join the domain, and since the PC will do a device scan on initial boot up, it's super handy for hardware independent imaging.
The 50,000 foot view of my old imaging process:
Sysprepped image dropped to the client PC
Tokenized sysprep file dropped onto the freshly imaged PC with unique computer name
Drivers for the specific model dropped to the PC in a standard drivers folder
Client PC reboots, gets named properly, loads the correct drivers, and joins the domain
Client PC reboots one last time and is ready for deployment or further software installs if needed