I used the tool to unlock my Focus S the first night I had it. I just counted the sideloaded apps on my Focus S, and I count 11...and I think there may be one or two things that got sideloaded that don't actually show up as apps in the list. Also, I loaded up a few more xaps that I have since uninstalled, like the HTC flashlight, and the LG panorama setting, simply because they didn't work on my Samsung...point being that I have had more than 10 at one time...
BUT...I also took advantage of a hack found over on XDA that enabled the stealth tethering which apparently interop unlocked me as well...which apparently is the key to getting around the 10 app sideload limit...
I am sure there are others smarter than myself that can help shed some light here, as I am still kinda new to WP...