The Verizon On-Line Help section has an automatic "Tweak" for FIOS users. It adjusts the MTU and Rcv Window settings on your pc. It works without any manual input from the user. You can also revert back to your previous settings with the click of the mouse. (This is what the installers usually use)
http://netservices.verizon.net/portal/site/msa/index.jsp?case=speed_optimizer.
Also, I have found that some NIC's will not automatically switch to 10/100 when hooked up to a 15/2 or 30/2 package, which will cause your speeds to hoover in the 9-10mbps range. Simply deleting your NIC and rebooting to install it should do the trick.
