Apple is the more reliable brand, not only in terms of hardware, but also software. Perhaps the biggest downfall is that Apple will try to persuade as much money from you as they can. For instance, you'll find yourself paying for new versions (iMovie, iWork, iDVD, etc) with release dates only 18 months to 2 years apart. Most users haven't fully utilized their current version to be wanting newer versions.
Sony and Toshiba are great too, hardware-wise, but not exactly software-wise. Although Windows 7 is out, I still use Windows XP. It's about the only stable operating system out there for Windows.
But, if you find a laptop you really like, just buy it.