This is my approach as well. This basically amounts to planning to throw one away anyway (http://c2.com/cgi/wiki?PlanToThrowOneAway) or rapid prototyping (http://c2.com/cgi/wiki?RapidPrototyping).

After coding the first implementation you will always realize things that you didn't anticipate that could improve the design. It's easier to get it working quickly, find the holes in the algorithm/design, then refactor it to be pretty and maintainable.