Generally an excellent price guide, has improved a lot in the last few editions with the addition of some lovely colour images or rare items, especially depicting some wonderful sleeves.
However, it is a Price Guide, and Guide is the operative word...
Certain genres are well under priced in my opinion (certain reggae, ska items, psych singles, library items and some NWOBHM).
It seems also that certain items are hugely overpriced, such as Cliff Richard and other early Rock and Roll items,and some British Jazz seems to have reached its peak..
There are also many collectable items that fetch good prices at fairs and on internet auction sites not even listed here... Punk singles for example.