I have a prospective client running on "Paymentech Tampa" platform, which is not TSYS. They want POS 2009 this fall. As much as I'd like direct integration, I'm thinking PC Charge is going to be our best option. We've deployed Slipstream as middleware for our hospitality POS package, but I've never seen it with RMS/POS.
I called Verifone's POS Development line, got an almost immediate answer from a friendly American (I know! Immediate PC Charge technical assistance!) and they didn't know of anyone who had come to them for support on such an integration.