I wanted to customize the datapager in silverlight to be able to change the pagesize after it is set and be able to change the UI of the DataPager a bit.
As there is no support for multibinding, I inherited DataPager added few properties and was able to get it to work. you should be able to change the number of rows displayed by changing the value in the TextBox next to “Show Rows:”.
The code doesnt have validations. for checking if the entered value is valid.
you can see a sample here and can download the code from here
Lee's corner 
Great job.
how about if i just want to load a page (10 items, rite?) each time? not load the whole ItemsSource?
Were you able to to get an answer for this,.. I am also looking an answer for the same
I might be too late to respond to this query but DomainCollectionView is what you guys are looking for. Follow this link for further details:
http://blogs.msdn.com/b/kylemc/archive/2010/12/02/introducing-an-mvvm-friendly-domaindatasource-the-domaincollectionview.aspx