I have used NSI for 2 years. at college we swoped nail systems to nsi in the last half of the year. Attraction and Balance.
I really like the product and results, for my clients they are ideal.
Some of the products hav so much choice (coloured powders) so if you have clients who like art or extra details everything is there. (The illusion gels soak off, they sound very good i havent used them yet)
I have however tried a few other companies liquid and powder systems, the moxie from cnd was very easy to use and results were long lasting (but i am still with nsi)
hope this helps, x