They are one of the larger gateways - having two datacenters. They also offer a merchant account as well through their site. Bank of America is one company who usually pushes merchants to their gateway. Changing gateways can be cumbersome at times. Are you using Payflow as the gateway or Paypal as a third party processor?
Their reputation is that they focus more on larger merchants then payflow or authorize.net and therefore have less integration into shopping cart systems typically used by small merchants. What software does your online store use?