Seat of the Pants Method:
Has your electric usage/bill changed significantly?
Seems like I recall an IEEE Power Engineering Society Transactions paper a few years back that also cited measurable effects on analog watthour meters; think it was 5th harmonic, but wouldn't swear to it.
Surf IEEE web site for authors McGranahan, Emanuel, Orr, and/or Cyganski for the best and most direct links to this and other papers like it; can't remember for sure whether any of these people were the authors, as I now I'm thinking the paper might've come out of Georgia Tech (McGranahan = Electrotek & McGraw-Edison; others = WPI).
Elegant Method:
Do it the right way---
Get your Building Services department to arrange for installation of isolation PTs and CTs on your primary and downstream secondary panels, especially those with a lot of solid-state power supplies connected. Buy yourself a harmonics analyzer, plug it in, gather data, and knock yourself out by studying all the data you'll ever need/want and then some, sixty ways to Sunday!
If it ain't smooth, it ain't 60 Hz.