A short update of what I've seen so far.
The main change is that the web-interface (=how to get information out of/into the thermostat from your app (Homeseer, whatever)) has changed from Basic authentication to Digest. This means calculating MD5 hashes for sending username & password back to the thermostat.
However I did find remainders of the "older" API that's used in the NT20e (the one I have). I've checked only a few things, but from what I've seen it looks like the API has only become larger, but the already existing part has been left untouched. For example, changing the setback seems to work as it does on my NT20e. That's good News
Now that I've added Digest auth to my system, I can start firing HTTP calls at it and see what it returns!
More info later!