Yes, I use CO2 in my 45 and 30 gallon and dose a modified EI method. I use AH Supply CFL DIY fixtures on my tanks.
You just missed the Annual Plant Auction last month; 500 plants from common to really rare including Erios, Syngonanthus, Pogostemon, and a multitude of others. In fall 2011 we had Tom Barr as a speaker, Karen Randall (twice), and next fall Christel Kasselmann!
There is a 'mini-auction' at the end of every meeting with plants and fish provided by GSAS members. Check out GSAS.org when you get a chance.
I picked up my regulators on Craigslist as well as my tanks. Here is a link I spotted earlier this week; if it is still available it is good deal. Regulator and needle valve, all you will need is a CO2 tank.
Are you running Nano tanks? Otherwise the cost of repeatedly refilling those paintball cylinders will cost a whole lot more than getting a real regulator. Also, paintball regulators are not known for their reliability. I have one 15# tank, with a splitter and two needle valves and I can run my CO2 24/7 on both tanks for 10 months. If they still have the one they listed on Craigslist maybe they will take a lower offer?