Yes, the back side is getting racked up like the front side. The top panel that has four 4" muffin fans is being removed since the blowers and servers themselves create significant enough airflow to power the hot air up through the top of the rack. By the weekend there will be 10 servers on the back side. At my current rate I will have that rack full in 3-6 months.

The only thing that happens on the back side is power getting plugged in. The cords I use a 3 to 5 foot cords (depending upon placement in the rack). Whenever I have to pull a server out I pull the ethernet cables out through the rack ears, unbolt it, and just slide the server out. I need to go through and cut all the warning labels off the power cords to prevent a potential snag. So far, on the dozen or so I've pulled out for various reasons, the power cord just slides right out with the server. Maybe it is because it is all new but they really do seem to have quite a snug fit. The biggest gotcha I have is if the vertical power strip goes bad. In a case like that I have no other choice but to pull one side of the rack down, pull it out of the middle, and put a new one in. The current rack I have pictured there is on the end of an isle so I can take the whole side off and reach behind them. I can fish the strip out that way and access all the plugs if I have to. So far I haven't needed to do that at all.

The USB sticks are a dedicated 1khz hardware timer that is used by Asterisk for audio framing and transcoding purposes. It allows me to run the servers at a higher load without audio quality issues as the dedicated timer is not dependent upon CPU load like a software timer is. It translates into about another 15-20% of usable horsepower before the system get overloaded in other areas.

The servers are SuperMicro brand. It's the only brand I use or will sell as an enterprise server. The current hardware recipe is as follows:
x1 Intel 2.33Ghz Core-2 Quad-Core CPU
x1 SuperMicro Motherboard
x1 Crucial 4GB (2x2GB) ECC Memory
x2 Western Digital 160GB 2.5" Hard Drives
x1 SuperMicro 10" 1U front-IO case
x2 40mmx28mm 28CFM fans (LOUD buggers)

I'm using Linux RAID for ease or portability with the hard-drives. I can also add another 4-gigs of memory for a total of 8 if need be. Out of 100 servers I've built and used I have only had 2 failures. One was were the second ethernet port quit working, and the second one was a failed power supply after a few months. The second failure all I did was pop the hard drives out and throw them in another chassis. Only took about 15 minutes once I got my hands on the chassis.

If you want the actual hardware BOM just send me a PM. I'll shoot it across to ya along with a few instructions on mounting the fans (requires some decent tin snips).