I've been fresh water flushing my TAMD41A's for about 18mnths now. Prior to buying WineDown ~3yrs ago, I was a 40year outboard powered rec boater and as such, flushing motors after use was just 'what you do'. I always felt kind of weird and 'not finished' when packing up the 'big boat' before I installed the flushing hardware (quickflushvalve.com).
A few teething problems initially - my SB motor wouldn;t draw from the bucket at idle but the port side would. Both were recently fully rebuilt raw water pumps. I'd have to give the SB motor ~1100rpm to get the water pumping. Absolutely no 'quirks' like this at idle when running normally with raw water. I solved this issue by moving the bucket up from the bilge to the cockpit - thereby using the help of siphon to keep the flow up - works great and now draws at idle.
I let each motor draw fresh for about 10mins (or a cigarette and bit of a chat, or an odd job if no-one else helping) each. I'm convinced it's beneficial - how could it not be? Certainly makes me feel better (after a lifetime of religiously flushing outboards post-use) anyhow.
Hopcar - your 'use flush system as a bilge pump' idea is not new FWIW - the quickflush system i purchased came with filters that I can attach to the hose for exactly that purpose - emergency bilge pump - without introducing unnoticed flotsam from the bilge into the raw water system.
And finally - the one piece of advise I received from everyone I spoke to about fresh water flushing (both the pro-flush and the 'makes no difference' crowds) was to draw from a bucket, NOT the garden hose plugged strait into the system - for safety.