I am still trying to understand this rooting thing. So can the Moto Droid 2.0.1 be rooted and put onto a Droid Eris?
The whole point of rooting a phone is to give you administrator-rights to the Operating System. It's not a way to copy the capabilities of one phone to another.
If you don't know what you're doing, you CAN and WILL destroy your phone. Verizon will NOT help you if you screw it up -- in fact, they will probably void your warranty if they find out that you were trying to root your phone.
Having said all that, you gain some really cool features with a rooted phone. Total control over EVERYTHING on the phone, not just what the Google/Motorola/Verizon developers want you to have control over. There is also a small selection of apps on the Market (and elsewhere) that will only run on a rooted phone.
But if you're liking the feature-set you've got on your phone, and don't really feel the need to mod it, then rooting is probably not for you.