Generally, one of the big things that hurt SL was the large installer size and time it took to install. These things all ‘add friction’ between someone signing up for SL and actually using it.
It appears that, despite once being relatively small, Interface installers are now 116MB. This thing isn’t exactly downloading fast, and although we all have broadband in 2015, we don’t all have fiber. It’s currently going at around 219 KB/s, with ‘6 minutes remaining’.
I’m not really an expert in these sort of things, so I am unsure as to what can be done to streamline the installer for Interface.