We have had great success with the TSS. We just recently purchased our second resale contract (this time BWV). We called our sales rep, and she told us what the high and low price for BWV resales had been in the last six months, and we talked about contracts that had come available lately. We were thinking about OKW and BWV, so we go information on both of them and then waited for a June use year. We got an email with a June use year contract that we liked and made an offer. Our sale rep. called the seller, and our price was accepted within the day. The contract with marked as pending that day as well.
I found TSS very good to work with, and the closing took place faster than estimated. The sellers helped with that too. We were able to close in time to get a New Years reservation for BWV.
If we do another purchase, we'll TSS again if that's any help for your decision.
Good luck.