I own and operate two .45 Witnesses, a Colt 1911 .45, and a .45 24/7 OSS, so I can fully relate to your experience.
It took me awhile to get used to my .45 24/7 OSS's trigger, but having already owned a 9mm 24/7 Pro, probably not as much time. That stiff letoff will get better with time/use. I only have about 900 or so rounds thru mine so far.
Currently, I am more confident of longer shots with my other .45's, as they have smoother triggers, but I have also spent much more time shooting them than my .45 24/7. I hope to spend more time shooting my .45 24/7 OSS, if Ammunition supplies/Reloading components ever get back to normal. Not having the low shooting problem with either of my 24/7's.
Also, no magazine issues so far with the second or third generation magazines. My 24/7 OSS came with second generation magazines. Last October 2008, I got some third generation magazines from Buds Gun Shop (currently out of stock).
While I do like my .45 24/7 OSS, my favorite .45 is my 2004 vintage .45 Witness, and probably always will be.