Also, in the new version the exercises are not collected at the chapter ends but rather sprinkled throughout the text. I find this to be better. Solving exercises at the spot facilitates learning. Also, facing a long list of exercises at the chapter end can be a bit daunting. (I wish Jech didn't move all exercises to the chapter ends in the third edition. What was he thinking?)

The 2011 version contains a lot more. Also the approach is a bit different. In the new version Kunen does not hesitate to use model theory and topology to get results. This condenses some parts of the old book. Still, the new book is 75 pages longer. This means that there is a lot of new material. Especially, the chapter on infinitary combinatorics contains much more (including sections on small cardinals and elementary submodels). The iterated forcing chapter contains a section on proper forcing.

@ Prof. Paseman: Sometimes it is a good student who already knows the topic but nevertheless gets stuck at an easy problem. It happens. I've already worked on it long enough and unfortunately I do not have any more time to spare. So please do not prolong my misery by subjecting me to the socratic method. It is already embaressing for me to ask such a simple question. What I need is to be shown the answer so that I can see what I missed and move on. I guarentee you that I will learn from the answer given, especially because I am upset that I couldn't think of it myself.

@ Professor Hamkins: Thank you for taking your time to answer my question. You have been most helpful.