Have no doubt - joining views to views can be very problematic when the view definitions include JOINs. Typically, joining views that SELECT from only one table (as you might have when using views as an abstraction layer to limit access to the underlying tables, for example) won't suffer from this problem, though.

One way to see how much this issue is affecting your database would be to rewrite queries that join views to return the same results by querying the underlying tables directly, then comparing the execution plans, I/O stats, etc.