With 30% down, lenders look to the equity in the property and do not even look at credit.
Some good things about NOT paying all cash - such as, you can improve your credit score, like Deborah said; you can use the extra cash and put into some good investments, hopefully make more money than paying for mortgage. some extra money for raining days.
Make sure you do save the extra cash insteat using it for none essential things.
When you get a mortgage, make sure you are able to handle the mortgage, insurance and all other expenses for years to come. Don't get yourself in a bind again!