Its really more of a splat book than a new PHB. I would actually compare it to Complete Adventurer, but with more stuff about roleplaying. Compared to DMG2 which did basically expand on the DMG, If you liked Complete Adventurer, then you'd probably like it... if you didn't care for complete adventurer, then I wouldn't get it. Oh, and it has new base classes rather than new prestige classes (I think this was mentioned in the review).
Oh, and I think the whole book is actually not useful to everyone (beginer or expert), mostly b/c it covers such a broad area. ie if you are wizard, you'll find the new spells useful but not the new fighter only feats, and if a fighter vica versa. Or a beginer might find the rp advice more useful than the teamwork benefits, which would be reversed for old time players. Also there is the laughable line mentioned above, that you can 'treat yourself to a new character sheet' of your old one gets worn out, lol.