I think I am holding off on buying an XBR4 until I see what these new sets will offer. IMO, the Sony's 8ms panel is way too slow for a top of the line TV. The XBR4 may have 120 HZ, but I think that is only to compensate for the slowness of the panel. I have looked at panels with 6ms, 5ms, and 4ms response times and they all appear to handle motion better than any of the 8ms panels, including the Sonys.
This new Philips line seems to be approaching the Holy Grail of LCD panels. With a 2ms response time, 120HZ processing, along with the Ambilight feature, this set will be hard to beat in my opinion.
I have been looking for an LCD set with little or no motion blur or artifacts for the past month and I have concluded that this set does not yet exist. The Samsung 5271 that I had for a few days came close in this regard, but the reflective screen was a horrible thing to include on an LCD set. The blacks were fantastic on this TV but I could also see my reflection in those blacks.
Hopefully, we will see these sets in stores in April and May as stated and not September and October. Right now, I just have a wall mount with no TV. I'm not sure how long I can wait.