I think the extremes from both sides (PC & Mac) of the arguments are ridiculous.
I own a Mac Pro. Yes, it’s expensive, but it is built with Server Grade hardware, it has a three year warranty, it works without hassle or worry and if it breaks, Apple has an obligation to fix it.
With PCs (Custom or otherwise) you're not guaranteed amazing customer service where ever you go, pre-built systems (like Dell's) come with software bloat, Vista is OTT, slow and irritating, PCs never run how they're supposed to run and are always inefficient. The mainstream PC customers are patronized by stupid adverts selling them kit that they don't need. PCs are rendered out-of-date far too often, new components have far too high launch prices and spending thousands of pounds on a PC to play Crysis is pointless.
Having said that though, Apple annoys me via their obsession with the iPhone, which to me personally, is the biggest waste of space I've ever seen. It does nothing, repeat nothing, different to other high-end phones. It requires that you buy it with a contract, its flimsy, has no quick ease of use in the way that a simple phone with Buttons has and is mostly used by people who care about their social status and image. No-one in business would go near an iPhone.
Apple should concentrate on Mac's because thats where their most loyal customers are. Having said that, there aren't so much notable flwas with Macs themselves.
With regards to PCs as well, Microsoft XP is The de-facto standard OS for businesses worldwide. Microsoft has around 90% of market share with its OSes and Apple has around 10%. Vista is shoddy and runs slow, but that's because it has to be coded for an infinite number of configurations, drivers, components, etc. Apple doesn't have this worry but neither do they have the huge profit margins that Microsoft enjoys.
Fact is, there are pro's and con's for each side and each company. At the end of the day, PCs and Mac's have to be different because that’s the nature of competition. it'd be pointless and boring if Macs turned into Blue LED Gaming Computers and if PCs became sleek but boring.
I’m sure you’ll all find flaws in this summary and disagree with most of it (specially about the iPhone) but its just what I think.