It is hard to compare on price
I have this argument repeatedly with friends - and it's tough because while it's easy to spec a non-mac to, or above the specs of macbooks, there are certain things that are hard to quantify.
For example, Dell have just started using Sandy Bridge i7s in their XPS laptops. As they don't do 13" ones, I've had to compare the 15" ones, giving the Dell the edge when direct comparisons aren't possible.
Apple MBP 15", 2.2GHz i7, 4GB RAM, 500GB 7200rpm HDD, 1680x1050 screen, £1929
Dell XPS15, 2.2GHz i7, 4GB RAM, 640GB 7200rpm HDD, 1920x1080 screen, £1149.
Looks like a shoe-in, but this is where it becomes interesting.
The Dell comes with 2GB GT540M graphics, the MBP has dual graphics cards - main one being the 1Gb HD6750M. It looks as if Apple has this one based on cursory glances at benchmark websites.
Another thing it's hard to gauge based on manufacturers details is battery life - Apple are generally at the high end of this benchmark, too.
The main thing, however, is resale value - I'm a PC person, and always have been. Yet when I'm done with a laptop, it goes in the loft. The idea that it has any residual cash value after 2 years is alien to me. Yet I have friends who have even made profits over 6 months when buying Macbooks.
For me, the idea of upgrading every year seems like a colossal waste of time and money, but it's the only way I could justify a mac laptop. I think I may be overanalysing things here, though - despite the ream of figures I'd have created, I'm still susceptible to the "IT'S SO FLUFFY I'M GONNA DIE" sensations.