Back when I still had my Celeron 400, I just kept the entire case slid off of the chassis. When I got my Athlon 1.4 (Man was THAT a change) I kept both sides of the case off. However, although it does help with cooling some, I personally prefer to keep it closed up with a lot of fans unless working on it. Pet hair/dust used to accumulate on my equipment like crazy, which counters the effects of leaving the side panels off by holding the heat in. So, I find it to be rather counter productive. But that's just me...if you feel like blowing things off more than usual then go ahead and do it.
I've seen those tech racks before...the only real use I could see for them is if you are a pc tech and need to have things easily accessible, or if you're setting up a new system you could mount it on it before putting it in a real case.
I could just see my bird with that open rack though..she'd land on the motherboard and chew parts off of it :Q