It's a fantastic lens, I own one myself and highly recommend it. However; it can't realistically replace the kit lens, simply because the kit lens is a zoom with a relatively wide end that the 50 mm just won't be able to replace. That's not to say that you will get much use out of the kit lens, I think you would but maybe you would be just as pleased with a 50 mm prime.
If you wanted to try it out I don't think it would hurt, you can always go back and order the 18-55 mm kit lens later for about $80. You could also get the Sigma 18-50 F/2.8 which would be even better since it has a fast constant F/2.8 aperture. Another option (for considerably more money however) would be the Pentax or Tamron 18-250 mm lens, they are both identical so it doesn't really matter which of those two you choose.
I say do what you want, the 50 mm lens is a great lens and very fast, but I think that you may soon realize that having a modest zoom lens can be invaluable.
SLC
By the way: excellent camera choice you won't be disappointed!