In the Tower at Hong Kong we were required to give 2 minutes vortex separation for mediums following 757's on departure.It was introduced in their Mats part 1 some time ago.In the Uk it is not required on Departure.However extra spacings is required for mediums following 757's and certain other upper mediums down the ILS.I use that HK departure separation here just in case and certainly would not penalise someone for wanting 120 secs behind one of those things.
Also a friend who flys 744's reckons that the vortex behind a 757 is enough to throw a 744 around down the ILS.I think you're wise to give them a wide berth.