In my own experience (which is modest compared to guys like Greg I admit) I find what matters most in the decision to buy or build depends on the hardware they are offering in the pre-built systems. Most times its junk but not always. It seems to be getting better actually. The OS and bloatware it comes with matters too but not as much as the hardware.
Just finding out about the WD drive thing.... two WD drives belly up this month. One a 3 year old 300G PATA that had my system and itunes collection on it in my media machine that I built (I'm not about to tell my wife about your woodie) and the other a one year old 320G SATA that had me rebuilding my mom's system drive (bought that machine from Acer) from the ground up. She keeps finding stuff that I missed. Both machines were left running 24/7 to be fair.
I helped my stepson pick out and build a Q6600 machine last year that absolutely screams. It came as a combo deal from TigerDirect and in hindsight a better mboard would have been in order. We went with an Intel board with onboard graphics to keep initial costs down but you can't over clock the thing which didn't take him long to figure out. Its a bummer because what I read indicates that the Q6600 was the best balance of cost at stock speeds while having excellent overclocking potential. I guess the I7 will rewrite all of that soon enough though.
It seems that equal or better levels of performance can be had for a lot less $ now from the major manufactures and as leary as I have been of their proprietary hardware I recently bought a HP Core2 Duo laptop from Costco and I'm very happy with it. With the exception of my stepson's quad, it easily outperforms every other machine in the house. Its only 2G but has a great 17.1" (battery hogging) HD display with ATI Radeon graphics, a full 101 keyboard, usb, firewire, ESATA, PCMCIA, VGA, HDMI, wireless N, Gigabyte, Bluetooth, high def audio including dual headphone output jacks, a good webcam and built in mics, and dual drive bays. It came with 2 250G 5400 rpm drives installed but I replaced them with 320G 7200 rpm Hitachi Travelstar drives to make it a bit snappier. They are reputed to give superior performance while using the same power of a 5400 and it seems to be true so far.
