Both my wife and I have the Droid. I considered getting her the Eris, but #1 I want her to have a phone that is just as good as mine and #2 we can use all the same accessories.
* I started out with a Moto Droid, but downgraded to the Eris - the Moto was too bulky with the case, and a pain to get in & out of my pocket quickly (yes, that really did make me switch.)
I'm on a droid1 and my wife is using the Eris. She was not a fan of the looks of the Droid. Just last week got her rooted, romd, and oc'd. It runs great now compared to before. No sense now, but got her beautiful widgets for a clock and she's happy.