>>4
It's loaded with tons of legacy cruft, various hacks to maintain backwards compatibility, broken code paths (
http://www.lucidimagination.com/blog/2011/07/28/dont-use-java-7-for-anything/ ), only targets: x86, x86-64, arm, power, and power64 and only on mainstream operating systems (so much for "compile once, run anywhere"); doesn't have native support for unsigned integer types, does not have native support for simd vector types (LLVM does!), only supports a heavy-grained sequentially consistent memory model which impacts the scalability of parallel code, no tail call optimizations, and the list goes on.
If Scala could be freed from the tyranny of the JVM, it would be decent. I'd consider moving towards it for certain things that I currently do in C/C++.