In exactly the same boat here. Been looking at the 40W5500 although not sure what the differences are.
The basic view seems to be that it's a great set generally, for the money, although there have been some complaints about backlight bleeding. Other places I have read that it's not a problem with this machine, which is confusing.
The problem for gaming is that the KDL 5500 series have input lag, probably due to the processing needed for 100htz. There is still apparently noticeable input lag even in game mode. Strangely the older 4000 series didn't seem to have any input lag at all, probably because of the lack of 100htz.
A couple of questions... are there any 100htz tvs that don't have input lag? Or alternatively, what's the best sub 100htz TV out there? It's hard to find the compromise for good movies performance AND good gaming performance.
Actually re-reading this review,
Sony KDL40W4500 / KDL40W4500U Review, input lag of 0-10ms in game mode (although this is vs the Samsung F96 which does have a bit of lag itself) is probably OK...