We have one 3rd party package right now for our C# project. It is 12.1m is size. The entire Java product is 7.5m in size. Ouch. This means without any support code, just a base library, we are already at almost double the size.
Part of the plan was to have the C# product on the Silverlight side be faster than the Java product. While I have always felt they will be similar in performance especially when most of the speed is related to data coming across the network, I now feel that things can easily be much slower if we have the initial download hit that becomes 4x the size of our Java product.
When I asked some buddies about this they stated they have never seem lean and mean C# libraries. Not sure why the code is not as tight, too much XAML? That should compress nicely but it is rather wordy.