After reading through this post on Reddit, which describes how the author worked around intentional bandwidth trottling, we decided to give it a try here and it has had a huge effect.
We recently upped our speed on FiOS to 75mps, but we were bummed out when YouTube continued to buffer like mad even on non-HD content. After blocking the appropriate caches, HD videos now fully load in record time, often before the opening credits on the video are over. I haven't seen a single buffering notification and videos play instantly. The difference is akin to what I felt when I loaded my first webpage after switching from my 56K modem to cable.
Anyway, it might be of use to some of you. All props go to Kestrel for finding and then implementing the fix.