JVM vs .NET

I'm relatively new to both the JVM and .NET and am learning Scala and F#. I
was under the impression that .NET was essentially a later and greater
reimplementation of the JVM in a Windows-specific form. However, I've just
discovered some nasty caveats in .NET.

Specifically, if you generate and use regular expressions the obvious way
then .NET leaks memory because it performs run-time compilation to improve
performance but fails to garbage collect the generated code when it is no
longer needed. There are workarounds but I've yet to see a solution that
can even garbage collect code under .NET properly, let alone an elegant
solution.

So I'm wondering what the JVM crowd have to say about the relative
deficiencies of the JVM and .NET. Does the JVM garbage collect code
correctly? Are there glaring flaws in the JVM?

I'm aware of the array covariance problem in the JVM.

-- 
Dr Jon D Harrop, Flying Frog Consultancy
http://www.ffconsultancy.com/products/?u