Best to worst, from top to bottom.....
Panasonic Toughbook \ IBM-Lenovo Thinkpad
Macbook Pro
Macbook \ Dell \ Asus
Acer
HP
Gateway
Toshiba
Sony
The toughbook is indestructible.
The thinkpad is repairable, fast and sturdy with many features, including docs and 2 mice....
The macbook is sleek and small, but not as repairable and not as feature loaded as the thinkpad
Interestingly, both the macbook and thinkpad run mac osx fairly well because they share many of the same components.
Look for long battery life, like a 9 cell battery...which IBM\Lenovo has a special on....its a 7200 mah batter as compared to a 4800 or a 5200 mah battery from apple which cannot be expanded...
Some thinkpads have workstation level video cards if your going to do graphic design.
Nvidia cards have higher compatibility than ATI.
Intel has better battery life+performance than AMD in the laptop line.
You want bluetooth, because its only a $30 upgrade, half as much as a usb dongle key and it doesnt stick out....you can use bluetooth mice.
Roll cages make the laptop crushproof and usually is accompanied by accelerometers so the laptop knows its orientation (toughbook, thinkpad, and macbook)
IRDA is nice if you have an old pda or phone with it...or just wanna change channels with your laptop.
You really dont need Wifi-N since its still draft, so it may become useless....why pay extra...
The thinkpad and macbook have built in cameras
The toughbook and thinkpad have touchscreens
The thinkpad has a fingerprint scanner from upek.
Thinkpads and some dells have a trackpoint fingerstick in the keyboard so you don't have to use the touchpad in a confided space, like a train.
The macbook's touch pad is multitouch but nothing when compared to a touchscreen.
Toughbook and thinkpad have steel hinges.
Toughbook is waterproof and bulletproof...literally...
All the top three have some additional keyboard illumination.
Macbook has a backlit keyboard which makes it hard+expensive to replace.
The thinkpad has a frontlight keyboard from a light built into the top of the screen.
A lot of laptops, including thinkpads have special bookstands and docks....
Don't get a branded laptop bag, all it does is tell theives what is inside.