If you ask any project manager what's the worst thing that he can do to manage his project's, he'll tell you "using Excel to schedule and manage the project".
MS Project is way better at that and Excel is really not made to manage projects. Problems with Excel will start one you have change requests, how can you handle them?
I'm a contributor to PM Hut and one of the common things that project managers tell us is how Excel "ruined" the project (of course, you might think that they're blaming the tool, but when you start hearing the same thing over and over again, you will start wondering).
PS: Glenna's work is perfect, and I'm not criticizing it in any way (as she tried her best to make Excel work as a PM software), but again, and in my opinion (and the opinion of many other project managers), Excel is just not made for project management.