I've spoken with a few reps who have talked to higher ups in Panny and they have some strong statements they have made about the AX900. Coming from someone who has bought two Sony XBR 950B sets and replaced them ea 3 times only to have one that was ok on panel defects, I'd definitely say don't bother with Sony. Many others like myself have had several swaps done and many of us have returned them. Even the delivery guys commented how many Sony TV's come back.
Having owned a Panny Plasma before, VT30, I'd say if you are not a gamer, don't mind babysitting the set, are ok with buzzing, rising blacks, and higher amounts of heat and power usage then go the cheaper route. I liked the uniformity and off angle viewing with Panasonic. However, I game, I have kids, and don't like the other aforementioned issues. Which is why I think Panasonic has something to prove with this set, and companies with something to prove always grab my attention because there seems to be a higher focus on quality, hopefully.
I know this AX900 will have a mini display port capable of 60fps at 4:4:4, will have a 3GHz Quad core processor able to supposedly do backlight calculations real time (maybe have acceptable lag of 40ms in gaming?), and also has an IPS panel and a design that looks high grade.
Samsung had a lot with their panels, except higher input lag and being edge lit. Sony TV sets look cheap, feel cheap, and are laden with QC issues. So I'm happy to wait until this set drops as it's my only other option until the 15's come out, and I need to replace my two sets. So here is hoping.