I've got both Windows and Macs in my life (currently a Thinkpad, Macbook Pro, iPad, and iPhone), and I get to play with loads of hardware as part of my day job (mostly Dells, ranging from fairly inexpensive desktops to high end Precision workstations). In most aspects, I'd say my Thinkpad holds its own just fine against the Macbook (though it has several significant advantages in hardware including an SSD, slightly faster processor, and more memory), and both are quite reliable; the Macbook is nicer to look at though
As far as the Dells go, they're hit or miss, even among the heavy duty workstations. For example, about three or four years ago, I had a batch that had an ugly tendency to eat memory. I'm not exactly overly enthralled with the component quality that goes into them either; it's certainly nothing to brag about next to a half decent custom build. On the upside, they're cheap and they support their product (at least on the business side).
