I bought "Rapid GUI Programming with Python and Qt" (Summerfield) and "Programming Python" (Lutz) in order to help me write my first Python software application, a program whose development would require an understanding of Python, Qt, PyQt, and relational databases. I found Summerfield's book very useful.
The first few chapters brought me up to speed on Python itself. The chapters which dealt with PyQt were of course the most detailed and the most useful. I found myself getting frustrated with the "Dance of the Seven Veils": the book would touch on a topic briefly, explain how important it was, give an example, then hurry away to cover something else. By the time we got to the meaty, more thoroughly-explored examples, I was confused and slightly lost. Google filled in the gaps, so in the end it was all worth it.
In defense of this book's "A little bit of everything" style, I must point out that a toolkit of Qt's size and complexity cannot be covered thoroughly by a single text, in my opinion anyway. Summerfield took on an impossible task and did a good job.
All things considered, I think that Summerfield's book was worth the money. It rarely leaves my desk and never sits on my bookshelf. That's how useful it is to me.