However, if price rises in other exchanges, that can only be because of bitcoin demand exceeding supply. You cannot twist it anywhere.

I would therefore closely follow the pricing in Bitstamp and others, and that has been on a rise lately. It is tempting to think that the going price is $120 (Gox), but I would more likely put it at $103. If I were to buy, I would not try to send money at Gox to buy at 20% premium, I would use Bitstamp.