I owned the 2nd edition of PPR, which had some weak points, one of them being the lack of index. This 4th edition of PPR has a detailed index (10 pages), covers python 3.x and 2.6 (and also applies to 2.7), the matters have been reorganized and improved, and thus the contents page now is much more useful. The prose is excellent: neither very terse, nor verbose.
90% of the time I work in python solely with PPR, and the remaining 10% of time I consult David Beazley's excellent 4th edition of
Python Essential Reference (Developer's Library) for getting the "dirty details" in python and in the numerous available libraries there described. Thus, PPR is more than a mere pocket guide: its 200 pages indeed correspond to a valuable python single reference for seasoned programmers coming from all backgrounds.
All in all, PPR is truly a swiss knife for every Pythonista.