I also spent some time this weekend looking at an SZ at Best Buy. I liked the screen, I own an S380p and the SZ definately has a better screen than mine (brighter I would say). The keyboard is something that prevents me from wanting to upgrade. It is a negative issue, the keys are flat and the homing marks on the F and J keys are little dots of plastic, not a bar like most keyboards. My first impression of the model I saw at BB was that the keyboard looked and felt like one of those touch tone phones from the 80s where the numbers were on these giant keys. I think Sony was trying to make the keyboard easier to type on by making the keys flatter and larger.
Two other observations: the machine I saw had been on all day running a screen saver, I noticed no heat issues underneath or on the palm rests. The processor was the 1.8 duo, throttled to around 900 mhz.
Finally, the hard drive failing is troublsome. I owned a thinkpad t43p which also had this active drive protection, and it constantly came on when ever you moved the notebook. IBM had numerous failures of their 7200 rpm drive because the firmware on the hard drive needed up dating. I remember reading posts on thinkpads.com to immediately inactivate the active protection or risk having the HD fail. I am hopeful this is not the case with the new SZ models. Regardless, I am a bit bummed about the keyboard so I do not think I will make my next purcase an SZ. I appreciate everyones comments on this thread, it makes buying a new NB a much more informed decision.