Hey Dirt - that is choice - I too utilized all threaded PVC nipples for my build - the schedule 80 is nice - stiffer, with a thinner inner diameter (rated at 210psi vs schedule 40 rated at half that)... but the gray color just looks so choice with the red sprayers!
Just a clarification on the oscillating fans - I leave them on all the time - they actually help to stir up the CO2 as it is heavier than air and wants to float to the bottom... try placing an oscillating fan on the floor aimed up to mix it up even more! Now your exhaust fan is another story... you want to be sure to turn off your CO2 when you exhaust... good news is you don't have to exhaust as often with CO2 (AC is pretty much mandatory). With a CO2 gen, some people let it run all the time as the cost of generated CO2 is relatively cheap. Have you guys seen this?
http://www.youtube.com/watch?v=_SDorIv81CA
I have one on the way for a new room... I wanted to use one a few months back - but I did not want one sight unseen. My local shop kept intending to get one in for me to check out, but that did not happen... I ordered one last week - I hope I don't regret it! The same company makes some cool 6" inline water cooled elements for your AC reflectors; do away with ducting AND add cooling??? ...their stuff seems almost too good to be true - I hope that isn't the case!
Look ma - I got the DirtHawker version! No glue, no cutting!