I've a friend who gets ~130 servers or 0 servers. If he gets none, he restarts and gets the usual 130-ish.
I get around half of the servers he does. Typically 55-75 servers, definitely averages at 60.
Now this might sound crazy to some people reading it, but I was once creating the server browser for a video game where I had the UI update on each frame to display the server list. Never thought there'd be more servers than the framerate in a pre-alpha test. Yet, had there have been, I'd have had the same problem in that project as I'm having with Sandstorm now. Not necessarily. suggesting this is the issue, but I'm running around 60FPS on the menu... Just a thought.
Anyway, this is a massive problem when trying to join a custom server as I find myself refreshing for 5-10 minutes until I finally see it and can join.