i've got a 5" GI and love it. i was looking for a basic, inexpensive platform to build on, and i specifically wanted a slide that did NOT have a lowered, flared port. i really hate the GI sights, and couldn't wait to cut the slide and install trijicon dovetails both F and R.
starting with my stainless GI, i added a match trigger (w/ quality trigger job from highly ranked 1911 comp shooter), ambi safety, delta hammer, sear, checkered mainspring housing, 2 pc guide, guide plug, ext mag release, ext slide stop, beavertail, silver alumagrips, checkered frontstrap, trijicon NS, tightened everything up and polished it. looks so good i can't bear to carry the damn thing now. shoots like a dream, and looks sexier than Sharon Stone in a leather teddy.
my next round of mods - after a couple thousand rnds - will include a new firing pin, ejector, extractor, heavy duty recoil spring and buffer, more trigger tuning, and a match grade barrel.