agreed
however, not only planning well but sticking to that plan from concept to delivery is important.
i worked in an environment once where the dropdead change deadline was Dec 31. the project manager was still letting the customer make changes in march.
the amount of regression testing and QA we had to do with all the changes was enormous and management wondered why we got 2 months behind even though we were working 55-80 hour weeks.
execution of the plan means making sure all things are being done right...not just that it is designed "good enough" and that you put tons of hours in to get it completed.
i've had both great PM and bad PM...it does make the difference.
