Whether you agree the iPad needs a stylus may depend on what you intend to use a tablet for. I think not incorporating pen and ink in the UI was a mistake.
It seems odd to me that Apple would even adopt the "pad" metaphor for something that cannot be used as a notepad. Afterall, the iPad is incredibly deficient when it comes to easy text entry...so is the iPhone by the way, but the iPhone is a cell phone.
So for text entry, you get no stylus or pen/ink functionality and if you really want to type something (other than a twitter message or brief email), you are expected to use an external keyboard.
I will not be surprised to see the iPad initially blow out of stores, but I hope Apple recognizes that their tablet ain't no iPhone.