I had my Hitachi 57S500 done last year by Gregg and it is a night & day difference.
Colors are so much more realistic and he does a great job with focus. convergence, and even put duvetyne(black cloth) inside to cut down on the reflective glare of the painted black chip-board the cabinet is constructed with. I also had him take off the protective screen(no kids here) and it cut room reflections by 90%.
If you really into watching your TV, then have it done. You will be pleased.
Gregg was in my area last March of 2005..........my Toshiba HD CRT RPTV still amazes me....it was great meeting with him as well. A friend of mine also had Gregg do his ISF sometime in 2004 & then had it re-checked this past year by a guy in DFW @ LionA&V (& I think his name was Steve). He was very pleased with the re-check as well.