I bought the 15″ titanium powerbook several years ago and just recently replaced it with a new 12″ powerbook (aluminum).
The keyboard, although being the same size, feels quite smaller. The new keyboard is silver, not black, and doesn’t seem to flex at all. I just ordered the iSkin Protouch keyboard cover for this laptop, it should prevent candy and dirt getting under the keyboard. I could never keep the last laptop clean enough.
The 12″ display is not as crisp as the titanium’s 15″ LCD. This bothered me at first, but I no longer notice it unless I have it next to a better display. It’s also not a cinema display. I believe the LCD in the 12″ is the same part from the ibook line, which is less expensive. Probably explains the image not being as sharp as the other powerbooks.
Maybe an hour more juice in the battery over the tibook. I can squeeze four and a half to five hours depending on how much I have the screen dimmed.
The corners of the 12″ are rounded, compared to the square shape of the tibook. Besides looking nicer it’s more comfortable in the hand. I don’t see any evidence of painted plastic like the molding of the tibook. I really like the placement of the vents between the lcd and the base, no matter how I lay this thing down the vent won’t be covered. Oftentimes in the tibook the vent would be covered and the fans would spin up.
Speaking of fans, it seems to turn on more frequently than the older titanium. Overall I’m really happy with it– but I can’t wait to get something faster and a couple big displays.