I have been running zeo on my 300g since November. Yes it does get expensive when you start adding the stuff beyond the basic four or five.
I have seen improved color, and growth...but I can't say it's because of the zeo or my improved husbandry and stable chemical levels. The thing that bothers me about zeo is that there is absolutely no controlled testing to show that it is of any benefit. It's like my adding ten new things to my tank and claiming that the improvements were caused by numbers 2, 6, & 9. How do I know that? I don't?
I have seen a lot of very, very stunning zeo tanks, but I have also seen a lot of very stunning non-zeo tanks. The thing is...there is scientific data supporting why the non-zeo tanks looks so good. When you look at these stunning non-zeo tanks, you find that almost all of the stunning zeo tanks utilize the same husbandry and high level of maintenance as the non-zeo tanks. The only difference in most cases is the zeo.
I agree with Eric, it's not as important what system you are using, but rather that you are using that system at the highest level possible.