I tried priceline a couple of months ago to get some tickets from SFO to New York.
My offers were rejected.

HOWEVER:
a couple of weeks ago, I bid $350 for a ticket from SFO
to Tokyo. It was accepted and the whole thing cost me:
350
54 tax
---
$404

The flight was on ANA, and Ana gives you a 20,000 Yen (~$180) gift certificate on top of that. (as a promotion of starting service in San Francisco). And I still got FF mileage on United.

The second best deal I could find were AA e-fares for $454, but I could not stay as long as I wanted (only 8 days).

Conclusion:
I am satisfied and will try priceline again.