All the T-series have had metal exoskeletons, which are why they are stout. Starting with the T60, the screen has a magnesium cage around the back of it designed to have a big guy hit it with a baseball bat without hurting the screen's functionality. Starting with the T61 there are drain holes in the keyboard - you can spill a drink on it and the drink will drain through the holes into your lap without touching circuitry. Also, anything T60+ with a dual core processor will stomp the living shit out of a P4 based T3x/T4x, you would be very happy.
My T61 has an 80 gig HD, I thought it was going to be fine for a dedicated tuning laptop, but the recent 2009 edition of OnDemand5 is 74 gigs so there goes that bullshit idea. IDK but I also see no reason why it wouldn't, if the T4/500's are like the rest of the T-series family (including my T61) the CD drive is actually an "Ultrabay" and you can remove it to hotswap a second HD, or a floppy drive, or another battery pack. It's probably the way I should go.