What did Apple do?!

[dante@sisna.com]

Our MBP 17", 2.6, 4gig, 200gig 7200 rpm gets between 3.25 and 4 hours under heavy load (meaning networked, bright screen, processors running moderately).

We've never tried a light load.

 

[snickelfritz]

So in your opinion, is this why the RAM is soldered to the board? I can't think of any other reason to do that.

It is cheaper, faster, more compact, and more reliable to solder the RAM directly to the board than to attach a slot and insert a separate module.
There are simply fewer components and less potential for failed connections involved.
Every splice and connection in the data path increases the potential for signal loss, and this is multiplied if the system is subjected shock and vibration on a regular basis. (almost unavoidable on a commuter train, for example)