Bluestraw: all 3 of those TVs have received HDTVtest "Highly Recommended" awards. I think the fact that all three of them are using the same SPVA panel technology speaks for itself with regards to the quality of these panels. I think the best summary is:
Sony: slightly poorer video processing (no Film Mode detection), excellent usability/responsiveness, accurate colour, no 100hz, almost non-existent input lag
Toshiba: fantastic video processing, 100hz option, slight usability annoyance with 1:1 mapping, EPG could be faster, great looks/chassis design
Samsung: value for money, fantastic video processing, 100hz option, user accessible greyscale controls
You can't go far wrong with any of these - what would you be using it for?