Clearnail does work, even for quite severe infections. You have to be patient and keep up the treatment until your nail has entirely regrown, so it can mean buying more than one treatment, although a little does go a fairly long way.
Clearnail is quite a relatively expensive product but it is definitely cheaper than a long course of antibiotic or antifungal treatment which may or may not work.
A good quality product, well worth the buy.