The Nexus One experience....
...is that HTC clearly has the 2.1 code and has produced a nicely put together and polished phone, I've done some testing on it for work purposes and it really is rather nice. Makes my Hero seem a little behind the times, but only in terms of speed and the bigger display. Not all of the speed increase is down to the faster processor I think, the Android 2.1 code is understood to be significantly better than 1.5 was.
However, I don't think HTC are stupid, they know that having mentioned the updates in the US in 2H 2010 that this includes the delays of building customer specific variants. They have clearly had 2.1 a fair amount of time, and if they have the resource to update Sense UI (a major plank of their product portfolio after all across platforms) then I'm sure that they will have been ironing out the wrinkles. There are plenty of leaked 2.1 on Hero videos on Youtube, so they must be pretty close. I imagine that they would be quite happy to release around the time of MWC in mid-February, and there have been plenty of "early in the new year" hints too.
The one thing I really want it to have Bluetooth phonebook access profile so it works better with my car kit, but I have to say that the Sense UI means my Hero looks much nicer than the Nexus One.
And anyway, how much software actually makes it out when people say it will? I'll not notice the delay if I spend the timing sinking a pint or three :)