I just bought US2 through steam yesterday, and I find it very fun. I felt with this the same way when I first play mass effect (it was mass effect 2) the first moment I could travel to planetary systems across the milky way.
At first, I was a bit disappointed about not receiving US3 for free, but checking the video presentation with unity engine, I agree, US3 seems totally better than US2, and I am pretty sure I will pay for US3. (Besides, development is not free and after thinking and seeing the reason, I totally agree)
I have a question concerning future updates, and the implementation of new astronomic objects (for example, the new moons of Pluto, Kerberos, Styx)
Have you any plan to update discovered objects or renamed objects after US3 release? (renamed, I mean when an object is named like 2009TX300 and then it has a mythological/other name assigned)
Also, there is the Gaia mission to be launched this year that will begin to map nearby stars in 3D (its aim is 1 per cent of milky way stars (
http://en.wikipedia.org/wiki/Gaia_%28spacecraft%29))