This blogger finally got Ubuntu running on the T61P and describes the issues he faced.
Read them here
The official 7.04 disc could not boot. I believe this is due to the fact that the CD drive is connected via SATA rather than IDE/PATA. I've had the same problem with recent desktop machines, too. It's possible to get around this by setting BIOS (press F1 during boot) to use “Compatibility” mode rather than “AHCI.”
There are still problems getting X up, because the hardware is too new for the nv and even the nvidia drivers packaged with feisty. I'm using the unaccelerated VESA driver right now (which is surprisingly quick at 1920×1200).
Since I couldn't boot with the CD, I used my “Ubuntu on tap” setup, which worked perfectly.