Yes you can, in a very good way.
There are a number of data visualisation controls for Silverlight out there. The most easy is using the ones from the Silverlight Toolkit. (these are already included in Silverlight 4 / VS 2010). I personally really like the one from Component One. They are commercial (license fee, very decent price), but you can get a trial. These charts are highly customizable, and support zooming and panning out of the box.
If you want, please take a look at my Hobby project showcased here on vCampus, it includes a number of Silverlight charts using PI Data.
The basic outline is here:
Create a new Silverlight project in Visual Studio (pref. VS 2010).
Add a Service Reference to PI WebServices
Add a library reference to the charting library (Silverlight Toolkit or 3th party)
Call the service, and at the callback (event handler), bind the data to the chart. (you will have to browse some examples for the chart package you have chosen).
All and all, it's very simple to implement, you will have to do some research. With a few lines of custom code, you can already create Silverlight charts that use PI Webservices.