Yeah, its a quick swap out. Take the old one out and put the new one in. Ive only put 300 through it with the new RSA and my girlfriend experienced two failures to feed back to back. Not sure if it was due to her limp wristing (limp wristing could be a myth for all I know) because I had no issues. Prior to the new RSA I had about 1700 through her with no issues except two FTF's again but during the break in period (first 100 rounds).
Some have said that if you go and throw the new RSA in without also switching the extractor (the other supposed isssue with Gen 4's) then you will have extraction problems. My GF's two FTF's make me wonder but only time will tell I guess. I cant see why the new RSA would affect the old extractor, which for me was fine for the first 1700 rounds!!