My Monitor 70's I think have broken in some, they sound even better than day 1, typically I just left them playing music at fairly low volume all day long when I was home. Even on the old (relatively speaking) receiver I am using to power them, they sound great. Paired with the CS2 for movies (not yet broken in) they make the whole experience so much better. I have them placed about 9.5' apart, angled in towards me slightly with the CS2 about 12' in front of me. It's really cool to watch and hear things moving from one side to the other, or to hear little background effects that I never noticed before.
For music they sound even better, for all the money I spent in my car (Logic 7 set up using a JBL MS8 and Alpine amps) it just does not compare. Obviously I knew it would sound better in the house, but am still shocked at how much. I find myself either just watching movies/shows I have seen before, or listening to music just to pick up on details that I never heard with thte HTIB speakers. What's neat as well, is that they sound good enough that I don't think I need to upgrade my receiver just yet. About the only thing missing from my current one is HDMI, so I think I will just wait a little longer to upgrade. The front HTIB speakers are now being used as rear surrounds, and so far are working well in that position. I might upgrade those to some Monitor 30 or 40's down the line.