While it seems like a natural conclusion to jump to, Sony has never really made any comments one way or another if the new DualShock 3 would rumble while playing PlayStation 2 games. Website http://www.pspsps.tv/2007/11/dual_shock_3_the_pad_we_deserv.html is reporting that their brand new DualShock controllers are indeed vibrating with PS2 games; at least on a Japanese PS3. The games were Rez, OutRun 2006, and Katamari Damacy.
That was on a PS3 running the latest firmware, and if OutRun 2006 is vibrating, I'm willing to take a leap and assume the rest of the PS2's library (or at least the majority) will support the DualShock 3's rumble.
The control is very nice. Feels about three times heavier than the non-rumbling Sixaxis, which we're inclined to classify as a Good Thing (the plain Sixaxis feels too light). Rumbles like a tummy before lunch. And it has 'Dual Shock 3' stamped on its husk in blue type. The pad is also available in white, to go with the white 40GB PS3 model launched here today, but it looks a bit tacky because the sticks and buttons aren't white.