We use Sitelink. Have also used WinSen & Quikstor. I like most of the features of Sitelink but there are some things that don't work correctly and they are not willing to fix them. Have talked to them several times over the past two years and yet not change. Still better than the other two I've used.
We installed PTI keypad software at our two new stores. While the keypads work great with little trouble, the customer service is the worst I've ever experienced. They generally don't respond to you. The software's "event viewer" that allows you to see that activity on the keypads is much worse than WinSen. WinSen is very easy to use and search. As far as I know, PTI does not have this function which makes things difficult. In the end, I would never, ever recommend PTI to anyone. Just wanted to get the word out.