I've not tried the mycostop myself but I would be skeptical of some of the claims made by the manufacturer. Fusarium is a major problem in many systems of agriculture so if this stuff worked as well as they claimed, why have the big multi billion dollar companies not switched over to it?
According to a study done by the Centre of Competence for the Innovation in the Agro-environmental Sector in Italy found that:
"The biofungicide (mycostop) was very effective against Fusarium oxysporum f.sp. lycopersici and Verticillium dahliae in 2002 in artificially infested soils; however, in 2001 there was no statistically significant reduction of the vascular wilts compared to the control. The bacterial antagonist was not effective against Fusarium crown and root rot caused by F. oxysporum f.sp. radicis-lycopersici, when applied alone, but was less effective when applied with S. griseoviridis. Soil solarization provided good control of V. dahliae and F. oxysporum f.sp. lycopersici, but was also slightly less effective when combined with S. griseoviridis. A significant increase in fruit mass and a higher yield m−2 was recorded when solarization and the biofungicide were applied together in 2001. This indicated there may be a potential additive effect of the commercial biofungicide and solarization in increasing tomato yield; however, it was not consistent and generally not significantly different from the inoculated control."
The Ohio State Agriculture Research and Development Center found that "mycostop's efficacy for control of grape diseases has not been demonstrated."
Research conducted by Simon Fraiser University in British Colombia found that mycostop reduced the severity of some diseases in cucumbers, but found that mycostop "did not provide protection from (Fusarium) infection in these experiments." It was found to be effective against controlling Pythium however.
You need to remember that info coming from the company that makes these products is worthless - they are out to sell their product and will make wild claims to do so. It is always best to get your info from a non-biased scientific source. IMO the jury is still out on wether mycostop will do anything again Fusarium but most of the real science done on it at this point has found that against Fusarium it doesn't seem to do much.