Hi.
Contras:
First of all, project server installs on windows 2000 server only.
Second - it needs a SQL Server. For the real work, of course.
Pros:
It works just fine. Its easy to understand and to manage. Its integrates with other products (for me, the most important - is the integration with SharePoint)
It allows to organize an unified center where you can view all the projects and resources in a glance. And your boss will be glad to demostrate it to your clients, I think...
And its disciplines. All involved to the projects understands that they not in the shadow anymore... And the task has their dates and deadlines.
So, its good. Its realy good and comfortable and powerfull, and so on.
But...
Using a project server its not only install the software. You have to live in that way... And work in that manner...
If you would, then all be just fine.
Regards.