Remaining Issues: Many readers had questions and Issues the day that Lightroom 4 was released. Just a couple of days ago Tom Hogarty (LR product manager) did a post that reviewed a number of outstanding issues . So if you are having problems with Lightroom 4 I would first check Tom's list and then check the feedback forum that Tom gives a link to.
I have to say that I've had no problems whatever installing and using Lightroom. I think this is by far the best version of Lightroom ever! I love the Highlight, Shadow and Clarity sliders and additional brushes!
Video Training: By now there are several video series on using Lightroom worth mentioning:
I've not tried #3 but I have done 1 & 2 and they are both excellent! At the new price of $149 Lightroom is an essential tool for any real estate photographer!