I'll add that I owned a 1GHz PowerBook G4 (with a half a gig of ram) in 2003 to 2005. That computer was one of the ONLY computers I actually ever felt became completely insufficient for my needs after just two years. I went from "oh, I will check email and write word documents" to "oh, I need to design pages with PageMaker 6.5 and later inDesign CS/CS2" to "I own a camera and would like to view and organize the photos from that camera with it." -- and the machine just didn't keep up at all.
I don't know if my particular camera really was just a huge challenge, or if it was that sliding scale of expectations that really killed it, or if it was just the fact that the G4 was a processor that had already seen its prime time, and was honestly ready for a replacement. (The whole architecture, in 2002.)
Compare and contrast with every x86 machine I've owned since then. I don't know if it's just that x86 software is written better, or Windows with an anti-virus application have *that* much lower an overhead, or if it's that my needs (photoshop, virtualization, productivity + Internet) actually haven't changed as much in the three years I've owned my current computer, as they had in the three years I owned that PowerBook.)
But I'm willing to bet that it's a lot more related to the G4 than anything else.
(It's worth noting I have two x86 laptops from 2002. One's a T30 with a 1.8GHz P4m and (today) 1gb of memory. The other is an X24 1.13GHz PIIIm with 384mb of ram. In 2011, I wouldn't really consider either of them sufficient for my photoshop work, nor would either of them really want to try to virtualize anything -- but I suspect that if I tried, I'd notice a few things. the first is that either of them would probably do my photo processing more efficiently than the TiBook did. The second is that the T30 would be far better than the X24. By the time you got to the Northwood microarch, the P4 was on its way to becoming an excellent performer, and if you can get a Cedarmill or newer P4 or P|D on a 900-series or newer Intel chipset, then you'll have a very nice, well-performing computer capable of photoshop batching, virtualization, running newer graphics cards, and even running 64-bit code and using 8gb of memory. (On the 965 chipset, which admittedly also supports most of the Core2 chips of the Conroe and Allendale varieties.)
But that's all based on my usage, which existed in 2002, but 6mp raw photos were reserved for higher end (dual processor) Macs and PC workstations with >1gb of ram. (I now have a 12mp camera, and the X24 has successfully processed those photos, but I'll describe it as maybe not being the best idea ever. My Pentium M machine and anything Core2 and newer chews through it like no tomorow though. Which is great.)