Anybody have experience using these companies to process payments?

I've very familiar with Verisign's Payflow system.

It's a good product but priced very high compared to the rest of the market these days. (They used to actually have one of the most price competitive solutions on a price-per-value basis but then raised their pricing fairly dramatically and subsequently lost marketshare with respect to some other products)

Thanks. How about PayQuake?

These are just some of the other possibilities I'm looking at.