I feel like I should drop in here and add my $0.02...
I bought a 3930k when the C2 stepping first came out. I went batshit crazy with it: 32GB of ram (all eight channels at 1666mhz / 7-8-9-1T timings), a PCI-E RAID card that drives six 240GB SSD drives in RAID0, and the CPU itself runs at 4.5GHZ along with a 7970 OC edition card that can run reliably at 1150/1550 speeds. This thing is stupidly fast at basically anything you throw at it. I spent probably $$3000 on it including the Dell U2711 monitor, the 1KW platinum efficiency modular PSU and the cooling setup.
I bought this rig to be a multitasker. I certainly wanted to play games, but I also do a moderate amount of video transcoding -- ripping my DVD's and Blurays to H.264, or converting video or raw photos taken from my various family digital recording devices. I also wanted to do some VM work and wanted plenty of breathing room to do it all at the same time.
Well, to be honest, it didn't turn out that way. I ended up building a completely separate rig for my virtualization host -- actually, an i7-3770 with 32GB of ram and a bunch of commodity drives in varying RAID configs. All it does is VM's, and it has more storage than my "big rig". Handbrake still happens on my rig, but it also ends up happening on my i5-540m laptop when my wife is doing it (which is most of the time.) Sure, it takes longer on four threads rather than twelve, but she knows how to use the laptop and doesn't really care.
So, it ended up just being a gaming rig, which is utter overkill in every sense.
If I were going to do it all over again, I'd just rather buy the top-end "K" processor from the general consumer line, deal with a bit longer encode times in Handbrake, and pick up even better gaming performance. I considered swapping my i7-3770 for gaming duty and putting all the VM's in the 3930k rig, but the power draw (even at idle) is an order of magnitude higher on the x79 platform. And really, I just don't need the extra compute anyway.