I have EQ 7 and love it. I started with one of the lesser versions years ago. I didn't use it much, but when the time came to upgrade, I did just in case. I'm glad I did. Just so you know that if you buy a used version on eBay of say 5 or 6 I don't know if you can upgrade them. I think you have to be the first owner of the software to get the code to upgrade. I may be wrong here, but if you plan to do that, you might want to check into that.
It is well worth the money.
I still don't use it as much as I should, but I do use it for Round Robins all the time.