Not sure as I never used Namecheap before. One of the NC users can clarify probably. I know Namecheap has the reputation of being very reliable, somehow it never happened though that I registered a domain there.
Must say: 4 dollar for an .EU is very low, and even their normal prices of (I believe) just over 7 dollar are really cheap. That is 5 euro or so, you cannot get .eu much cheaper than that.
I hope that the lower prices and many promotions will make people embrace .EU, as I strongly believe in the potential of the extention.