Visual app benefits:
Pilots:
in most cases saves fuel, since you don't have to do an full instrument app expedites and simplyfies the process.
ATC: Expedites and Simplyfies the flow of traffic, and they give pilots the responsibilities of traffic separation and ground clearence.
IF you experienc radio comm failure on a sidestep manouvre (ie. JFK) you have to follow the missed app of the rwy you shot the app just as if were a circle to land app.
on a visual app you execute a pattern traffic @ 1500 ft (high performance A/C as opposed to 1000 ft for non high perf) and expect light gun sgnals from the tower.
of course you would squak 7600 and they would know you have lost your radios.
If its before any clearence for an app to any rwy IFR procedures apply.
you are cleared for any approach at the airport and you should adjust your ETA acording to your filed flight plan to within 3 minutes, even if this involves holding at the IAF.
If you have recieved a clearance or an "expect" any app, you should fly that one at your destination airport.