I don't own a droid, but my wife does. I've been playing with hers for the last 3 days and comparing it to my brand new 8530. I can say that my 8530 will probably get returned in favor for an Android phone. I think I like the Eris better than the Droid but we'll see.
The amount of free usable apps is just crazy. The maps program is awesome as is just about everything else. Google rocks and it's nice to see that they are behind this product. I think we'll be seeing them taking a large share of the market.