Found an interesting tidbit, regarding whether 4Gb will be addressable on the T6x. As noted above, Lenovo states in it's own specifications that only 3Gb will be addressable due to the limits of 32bit architecture. But, also noted above, this is incorrect insofar as 32bit architecture is generally concerned.
The following very good article, posted by BrianR in another thread, explains that some motherboards have more than 32 pins for the processor, allowing 4Gb to be addressable.
http://www.interact-sw.co.uk/iangblog/2 ... s3gbenough
So it all depends on the motherboard. And it is not in any way an inherent characteristic of 32bit PC architecture.
Still Lenovo says what it says and people in these forums, myself included, seem to have come to accept that only 3Gb will be addressable.
However, I was just looking at Intel's specifications for the 945PM chipset, which comes in the T6x, and it says that it supports "up to 4GB memory addressability."
http://www.intel.com/products/chipsets/945pm/index.htm
So that makes it sound like Lenovo doesn't know what it's talking about (which according to the article above is often the case around this confusing question). I'm excited to try it out. I hope I can find a 2Gb sodimm where I can return one if it doesn't work.