I do not use it but I have seen tanks with it (both online and in person) some are beautiful, some are not so. On average the ones I have seen are prettier than the average non-zeo tank I have seen, this may be due too the zeovit system or the individual. The best zeo tanks I have seen online are on-par with the best non-zeo tanks but I cannot say I think they are better. I Have never used it but I do not believe that all of the things zeo-users are seeing are false or non-zeo related, in other words I think there may be something to this zeo (threw that in there for you zeo-guys
) and the quickly building zeo-community is very helpful and supportive for the most part, even to non-zeo guys, in most all forums they are involved in and the zeovit forum. There has been controversy but dont let that dissuade you, it is really only a select few and everyone else on both sides is very civil ime.
Is it worth it? depends on where you are at now and what your expectations are. For me I have not seen in zeo tanks anything that I have not seen in others or my own for that matter. But I also have not used it so I do not have first hand experience of the change I would (would not?) experience on my own system.
Best bet imo would be to meet up with another zeo-user (jsbzmcdaniel, ect) and see if what they have is what you want, and if so try their recipe.
-John-