The X60s (as with almost every Thinkpad) has a Magnesium top lid and bottom that will block (or severly limit) wireless range. That is why if you look at a Thinkpad lid, you will see a few areas that are grooved sections-these sections are regular plastic and the antennas sit behind them.
Also, Lenovo usually has two or three different types of wireless cards-either Intel or Atheros based. The Atheros are power hungry and run hotter, but have better range overall than the more efficient Intel based cards.
I have a T60p, a T61p, and have owned an X61 tablet. I also recently picked up a used Macbook off of ebay to mess around with (really liking it by the way!) and the wireless reception on the Macbook is no better or worse than any of the Thinkpads.