I've used the bag for both squash and tennis, and since I cycle to my club fairly frequently, carrying a racket case along with a bag for drinks/balls etc. is cumbersome and irritating. This bag eliminates that problem!
Onto the features...
The main feature is the space for a racket, it's large enough and adaptable enough to hold any size of racket, be that squash, tennis or badminton (it also doubles as a great padded laptop slot - 15.6" screens and below) and there's a small pocket for valuables in the racket section.
The other two sections of the bag are small enough so the bag isn't dwarfing you, but big enough to carry 2 tubes of 4 balls, a drink, a towel (in the main section) and my wallet, phone, keys and sunglasses (in the foremost section).
The last feature I must mention is the padding on the straps - it's a really comfortable bag to wear day to day (I now even take it to work).