Oh no, say it isn't so! If you are using the standard menu items provided by the .NET framework (I don't, I use Infragistics NetAdvantage), and you create and destroy menu items at runtime, the memory isn't released.
This is one you need to be aware of. Google will give you a nice list of posts about it.
Of course, the Infragistics tools have their own set of problems - I'll post more on that another day. Perhaps after I've had a few drinks to prevent me from getting too pissed about them.