I too swore for upgradeability not too long ago. But then I realized something: I never really took advantage of it. Yes, I had added a hard-drive or two to my PC's, but that's about it. Vid-cards? By the time I wanted to upgrade, I had to get a new motherboard since connectors had moved on. CPU's? They went and changed the sockets, so I would have had to get a new motherboard. Same thing with RAM. In essence: when I upgraded, I practically got a new computer. It never made much sense to me to upgrade just one component, so I went ahead and upgraded everything.
Pretty much agree with this viewpoint on the upgradability issue. I remember when everything was supposedly "future-proof" (classic marketing term, now pretty much dead) and you could gain a lot from having the same machine and upgrading bits and bobs along the way - and everything was designed for this, because components were so expensive. Fond memories of upgrading from 4MB to 8MB to run Doom, and it cost a fortune to do so!
Last PC I had, I upgraded the graphics card eventually because I skimped at purchase time and it was only a year later. It's just coming up to 4 years old and pretty much everything in it is obsolete - AGP instead of PCI-X, old style PSU, original SATA, quite an old P4 socket etc. It'd be pointless to try and upgrade it.
Latest PC, I've already had it for 1.5 years and not really been inside it, and don't envisage doing so for its lifetime either. They're just so cheap now I guess, that it makes more sense to get a whole new one each time.
The funny thing with this is, if you get a new one every say 3-4 years, you end up with a build-up of the damn things and don't know what to do with them! No point in selling because they'd be worth peanuts, no desire to waste etc. This is where Macs are better for long-term economics as they can have a useful life of 6+ years at least and still sell for reasonable amounts second-hand.
I can see where people are coming from with the Mac graphics cards though. With a PC there's no need to upgrade anything *IF* you pick the correct components to start off with. The same applies to Macs - it's just that Apple haven't offered a suitable choice for those who want more beefy graphics.