There are millions of success stories with EI.
Not quite millions, it isn't just a case of changing the frequency of dosing and using EI endorsed nutrients that solves people's problems. Often EI dosing brings with it a whole bunch of new issues that are hard to solve, i.e. the green hair algae that I currently have which I cannot attribute a route cause.
I personally started the EI method along with pressurised c02 injection simultaneously after originally using the full range of EasyLife products which were absolutely useless. They were useless because there were no guidelines on how much to dose and the chelating agent in their iron products isn't compatible with hard water; something which they omit to mention on the bottle.
Once I started dosing EI nutrients (bought from Fluid Sensor Online) there was an immediate growth spurt in all of my plants but within a matter of weeks (when the growth spurt stopped), algae started making use of the nutrients; algae such as blue-green algae and green-spot algae formed and it was a very frustrating nuisance to get rid of.
I soon found out that it wasn't the new nutrients causing the algae, but a lack of water circulation in the tank, which I've remedied by installing 2 powerheads and 1 extra powerful internal filter. The result is that the nutrients gets transported to all of the plants well but I still have to deal with green hair algae, green spot algae, black beard algae and green dust algae, sometimes I need to deal with them all simultaneously.
So the good points of using the EI dosing method are:
1. It's more structured.
2. You are informed, in most cases, how much you need to dose on a daily basis in relation to your tank capacity.
3. Because you are aware of how much nitrate you are dosing (which you would not if you relied on EasyLife products) you can avoid tricky to remove algaes like blue-green algae which are caused by low-nitrate.
4. The micro-nutrients mixtures used in EI dosing usually tell you what iron chelate is being used so you can avoid wasting your money on mixtures with chelating agents which will not preserve the iron long enough in hard water.
Bad points:
1. You are more likely to have to cope with different kinds of algae (hair algae, spot algae etc).
2. More trimming will be involved due to thriving plants or to cut off bits of plants that have succumb to the algae in brackets above.
3. It is usually hard to transport the nutrients and c02 around the tank unless you have a good filter system and some powerheads. Some people like myself didn't purchase a tank primed for good circulation.
Fingers crossed it will work and not effect my discus also
The chemicals involved in EI dosing seem to be totally harmless if you are using potassium nitrate and potassium phosphate for your macro-nutrients and a standard EDTA or HEEDTA chelate trace mix. I personally only avoid TPN+ since they put ammonium into their product which will change into ammonia as the temperature and PH increases (according to chemistry articles; do a Google search).
'Millions' was a bit of Sarcasm there Mark.
