You Really Won't Know Until You Build It
Building new software requires an estimate for the project owner how long it will take (and how much it will cost). This is one of the dark arts in System Architecture. Unless you repeat a previous exercise 100% you are limited to guesstimates. And you NEVER repeat a previous project 100%, since there would be no need, just use last times results.And guesstimates are a waste of time!
On my Sunday blog tour (while Anthony and Ernest mess up the house <g>) I came across a very true quote:
" We spent so much time arguing whether or not it work, and when we prototyped it, it worked remarkably well. We could have saved so much time, if we had just build it sooner." Another reason to do paper prototyping.