I just sold my Macbook C2D for a Thinkpad T60p. I'll be one of the few voices here saying that I am VERY happy with my Thinkpad, which arrived this week actually. So my advice might be extremely biased or somewhat helpful. Hopefully it's the latter.
Some thoughts:
- The Macbook Keyboard looks nice, but my hands cramp after a long time using them. The smooth keys don't have much of a tactile feel and response, so it was difficult for me to type for a long time, and to type fast. For example, try "typing" on your flat desk for awhile and see how your fingers tire after awhile. My search for a laptop with an excellent keyboard led me to the Thinkpad.
- I spend a lot of time in Windows. Don't get me wrong, I love OS X and use it primarily at home on my Mac Pro. But at work I have to use Windows. The Macbook runs Windows XP with no problems. BUT, there are a lot of little quirks to keep in mind. Such as the two-finger scrolling was choppy for me, and the battery management is not as nice as in OSX. Also the backspace/delete key has different behavior in Windows. You will have to remap your keys, which is no biggie with Keytweak. If you will use OS X primarily, then definitely stick with the Macbook.
- Battery life. On the go, I got about 2:30 hours average use from the battery. The Thinkpad gives me 4:50 off of the 9-cell battery, and has room for a spare battery in the ultrabay.
- Ultrabay expansion. You can use it for another HDD or battery or Optical drive. I've ordered an extra HDD to install OS X.
Yes, you can run OS X on a Thinkpad T60, but AFAIK you have to get a seperate wireless card since no drivers are written yet for the one supplied with the Thinkpad (I'll find out when I try to install later this week).
- Macbook trackpad is very nice. The new Thinkpad T60's trackpad area is very small, and doesn't have two-finger scrolling. I'm getting more used to the Trackpoint Nav (red rubber tip) and it's nice because you don't have to move your hands from the typing position to move the cursor. But I do miss the beautiful trackpads of the Macbook and Macbook Pro.
- Durability. The macbook has a much more durable case than the macbook pro. But neither have anything on the Thinkpad, which is rock solid. Since I travel quite a bit, I felt like I had to baby the macbook. Even though I cleaned the Macbook religiously, the trackpad wore away where my index finger was (I blame the insane hours spent playing Warcraft).
- Gaming. The Thinkpad T60p with the 256mb card is very nice. I can run World of Warcraft with high settings and still get a nice framerate. On the Macbook, I couldn't run a lot of games, and warcraft only on lowest settings (still playable). The point is that having the dedicated graphics card is nice. Still the 950 card in the Macbook did everything non-gaming just fine.
- Light on top of screen. Not anywhere nearly as cool as the backlit keyboards, but the T60 does come with a LED that will light up your keyboard space at night.
- higher resolution. I get 1680x1050 on my T60p which gives me great real estate for layout programs and design/coding with Dreamweaver.
- Security. One of the big selling points for me was the fingerprint reader, which I can use to log in, or access websites like Gmail. Also, the Thinkpad comes with some nice programs from IBM (the Thinkvantage suite)
Most of these points are more comparable to a MBP, and honestly I was considering upgrading my MB to a MBP or a Thinkpad T60p, but luckily because of a corporate discount I was able to get a 8744J2U T60p for $1749, which came with a C2D 2.0Ghz, 2.0GB mem, 100GB 7200HDD, 15.4" widescreen WSXGA+, Windows Vista Business (yuck) and fingerprint reader. A few hundred more than a macbook for sure, but it's a beast of a machine.
Good luck. Either way you will end up with a very nice laptop!