I think it will be the same software, just some features not activated such as animated wallpaper, which is no biggie. I don't think we have anything to worry about, as the rest of it we will get.
I hope this isn't the case (i.e. the version of 2.1 for the Droid not having the same features as 2.1 for the N1).
If so, this is a significant issue for how Google is handling Android - too many different versions out there. So what would we have now ?? 1.5, 1.6, 2.0, 2.0.1, 2.1 (Nexus One), 2.1 (Droid)
Way too much fragmentation going on. If Google wants to really get Android to take over, they should almost mandate that phones be upgraded to current versions. Not sure how well that would work, but this is getting ridiculous. I'm sure developers don't like it either because so can't rely on certain features being available in specific phones.