Okay, lots of personal choices out there, but my CO2 system has worked great. None of it is cheap, unfortunately. I use a Milwaukee SMS 122 controller, JBJ solenoid, the Reactor 200 with Rio Pump, Dennerle check valve, and metering valve. No bubble counter- the controller reads (and sets) the PH. Adjust the KH (sodium bicarbonate) to 5 or 6, in my case, and the CO2 flows according to the chart. No test kits for PH, just KH, which is fairly accurate. Use Tom's reactor, and you might save a few bucks. I also use a timer and a couple of multi plug receptacles from Wal Mart- one, at the end of the chain, has all the electrical connections for the CO2 stuff. This plugs into my lights receptacle, which in turn plugs into my timer, which in turn is plugged into a 24 hour juice supply. Any maintenance to the reactor (cleaning filter and the like) is easily accomplished by killing the power switch on the multiple CO2 receptacle. That turns off the power to the solenoid and Rio pump, allowing me to withdraw the reactor from the tank. I purchased one CO2 tank from a welding supply place, and an aluminum tank from a hobbyist for $20.00. Loved that! A spare. Filling the bottle runs $10.00. Would suggest, if you don't have a bottle, to buy it from the supply place- they sometimes can get touchy about filling another's bottles.
Been pleased with the JBJ setup. You may also want to purchase some pieces separately and save a few dollars there from various suppliers.
Hope I didn't bore everyone with the hook up description.