So I'll chime in with a bit of a contradiction.
Despite the general 2-page or 500-word limit, I actually roughly doubled that in my PS that I sent out to all schools. Obviously this is OK for places like Berkeley that encourage 4-pg statements, but even schools that explicitly asked for 500 accepted me this cycle.
It's a bit of a game theory problem; if everyone goes 500, and you write an incredible personal statement that is 750 words long...obviously the 2 extra minutes needed to read 250 words is not going to make an adcomm really angry. So if it really enhances your application, I'd say do it. Before you send it in, you should, however, work very hard to cut away unnecessary content.
If you'd like to see the PS I used, I'd be happy to PM it to you. And if you want me to read over yours, send it over.