Hi Rick
I've been using Gigabit network switches & compatible PC's regularly for about a year now. In fact for most of my Adagio installs I spec gigabit networking as a requirement along with the appropriate computers, etc. I find that the performance improvement with Gigabit speed is very noticeable in Adagio, especially when using Job Cost or when running specific reports. It also helps in a gridview environment as well.

I also use a cable diagniostic tool made by Fluke to test the integrity of the cabling (eg, noise on the line, crossed connections etc.) It sounds like you have replaced your cabling, and I am wondering if you mean patch cords into the wall jacks or have you replaced the entire cable thart runs through the wall between the switch and PC?
As I said I have been upgrading my clients to gigabit, however I haven't been replacing the wiring that is run in the walls - that would rarely be cost-effective. I have kept the cabling at Cat5e and have still noticed a significant improvement in performance, but likely not as great an improvement as upgrading all of the cabling to Cat 6.

I recommend that you have someone test the cables (if there are any that you have not replaced) to see if there are any issues there. Sometimes cabling issues are not as noticeable in a 10/100 configuration but will surface in a 10/100/1000 environment.