The Chambers is the best available source of obscure dialect words, obsolete words from Spencer et al, and senses of ordinary words that have long been forgotten. It is this comprehensiveness that has made it the cruciverbalist's bible, particularly for crosswords of the more fiendish variety.
Qua dictionary, though, it is awkward to use compared to the various Oxford dictionaries (the Concise Oxford Dictionary, the New Oxford Dictionary of English, and the Shorter Oxford English Dictionary, in order of size). Moreover, the famously amusing definitions are far and few.
In short, buy this dictionary if you have to - i.e., if you while away your time solving (or setting) crosswords, or if you delight in our language's paths less trod. Otherwise, your best one-volume bet is probably the New Oxford Dictionary of English.