I wouldn't call a pressurized system on small tanks as overkill. As long as the method of reaction is good, a 5 lbs CO2 tank on a 30 gallon tank can last for quite a long time. All you need to do is watch CO2 input for a couple of weeks to make sure its stable, and that your CO2 concentration is at the level that you want it to be. After that, its basically a leave and forget kind of thing.
Don't get me wrong, DIY CO2 will work just fine for smaller applications. Heck, I had it run on my 15 gallon tank for a year. However, I can get lazy... and if there is a more efficient way at doing something, I'd go for it. The frequent maintanence that my DIY CO2 generator needed just wasn't for me.... so I switched to a pressurized system. Good thing too, because shortly afterwards, I upgraded to a 70 gallon tank
.
-Richer