Like others here, I have always rolled my own - Better bang-for-buck, better longevity...
Until recently. Over the last five years, my upgrade train has brought me inexorably into HP business class machines.
Now I got em all used. but there is a reason why I would rather buy into HP Business and not roll my own. And that is because I can't begin to buy the parts for what I can pick up nearly for free.
This elitebook I am on right now is an i7 with 16g of ram. I got it for under 150 bucks and all i have done to it is an SSD and a DVD-2-HDD conversion.
I just retired my last machine from my last upgrade run. an AMD AthlonII ... Now every machine in my house is HP, most are business class, most are running 16g of ram, All of them are over i5, and most are i7, and ALL of them bought for less than what the CPUs inside them would cost me new.
There just ain't no sense in building my own anymore. Not with so much awesome hardware laying around for next to nothing.
For the record: there are 6 desktops, 2 laptops, a notebook, a droid tablet, and a droid phone currently in my operational stable. That is down by one, as I retired one server/station in the recent shakedown.