I routinely use webpagetest.org, which you can use to perform performance tests from different locations, on different browsers (although only msie 7-9), with different settings (number of iterations, connection speed, first run vs 2nd visit, excluding specific requests if you want, credentials if needed, ...).
the result is a very detailed report of page loading time which also provides advise on how to optimize.
it really is a great (free) tool!
