Recently, i read few posts saying that Snells law fails for normal incidence...

I Disagree...

There are two ways of looking at it..

1)U have two media with u1/u2=u.

applying snells law, we get 0/0 form... This is indeterminate form. so, it can assume any value...

But, treating determainate forms can be complex and this is one way out- since it can assume any value, for your case it will assume the value of  the refractive index you consider!!!

Its difficult to agree, but its one way out...

2)now, looking in different way,

What does an indeterminate answer imply...

It implies the case is universal and irrespective of the media chosen, which is correct.. So, snells gives an explantion.. So. it holds...

Guys, please before saying a law is invalid or questioning it, think about the person who told it.. Do you really think that Snell hadnt considered the case of normal incidence? If it didnt hold true, Snell would have probably mentioned an exception to the law... Please dont explain this to a school teacher, they will never accept.. But, i bet, you go to any proper professor and they will agree with this argument!!!