From various sources I heard a bit about what Joakim Noah's off-season has looked like at least in regards to what he's attempting to do. The first line of business has been to add strength to play down low better. Obviously this is THE most important facet of his off-season, and Joakim appears to embrace his role as future center rather than trying to become the future PF.
That seems like the obvious choice but don't underestimate the Tyrus effect. Many tweeners seem to prefer to play down a size against guys they can overpower rather than up a size against guys they need to out hussle all game long. See Tyrus Thomas and James Johnson's comments on both wanting to play SF while both having far more minutes available at PF on the team.
Joakim's also worked on his post game, especially developing a plan of attack and working on how to read the situation with the ball. The goal is greater decisiveness and quicker, better decisions.
The tornado ball returns for another season, but he's working significantly on his lower body mechanics and overall balance. The goal was to fix everything about his shooting form except the tornado release this summer, and then fix the tornado ball next summer. The hope is by fixing all the minor mechanical problems in year one, that when the major one is attacked in year two he'll improve quickly enough to not have a year where he's shooting 50% or something ridiculous from the free throw line.
Overall, I've heard mostly glowing reviews of his off-season work to date, however, I'm not enough of an insider for people around the team / players to entirely level with me either. At this point, pretty much everyone has glowing reviews.
There's one story, I've got that suggests things may not be as pretty as the picture being painted, but it was an out of context off-hand comment in a story that was off the record and was merely a hint to a hint of trouble. I heard it on the last day of summer league, and while nothing directly was said bad about Joakim's off-season, the comment left me with enough doubts that I couldn't completely accept all the positives without some skepticism.