I don't necessarily agree that there is a definite divide between Pro and Home machines. I've seen loads of people using iMacs to earn a living with. I use an iBook for work. Similarly there are gamers who use a PM for anything but work.
You buy what you can afford and/or justify, irrespective of the label somebody else gives it. Yes, if I had the money I would buy a PowerBook, and it might help me get my work done quicker (though I doubt it, I can only type so fast).
With reference to the original post, if I had £999 to spend I'd get an iMac over a PM any day - its a no-brainer.
thanks for pointing this out james; it's interesting to see the comparison. Ignore the detractors - there will always be people who want to snipe for no reason.
I think ultimately, it's the buyer's decision. Sure, it may seem a bit daft to purchase a PM 1.8 when the iMac equivalent is better. But, if you don't have the need for an all-in-one system, the PM would be your best bet, especially if you have an existing monitor.
3 different machines, yes. 3 different markets, yes. The machines should be designed for their target market though, and a pro series tower being behind a consumer targeted machine is pathetic. Not to mention for the same price not only do you get better hardware, but a 17" LCD...(non reusable but still...i'll take a free 17" lcd with my power mac purchase thank you).