First of all, you can install applications that require root, such as drocap2, which allows you to take screenshots of your phone.
You can download Wireless Tether which allows you to give off wifi without paying for Verizon's extra charges.
You can even download AdFree that disables advertisements on all of your apps.
If you really want to explore and use the full advantages of gaining root permissions, go tamper with system files. You can change the color of your status bar, change the "Verizon Wireless" eri banner to something of your choice, and more!
EDIT: I probably shouldn't have used the word "tamper". Don't mess with any files if you don't know what you're doing; atleast until the bootloader is cracked and things like nandroid backups are available to be used.
Those are just a few apps and possibilities that are achieved through root. There's plenty more you can do, and there will be even more if/when the bootloader gets cracked.
Cheers.