> The biggest current knock against Java I see is JNI

Then you'd be happy to learn that it's been superseded by FFM: https://openjdk.org/jeps/454 (not in all situations, but in almost all).

> The second biggest knock is that the JVM is still kind of a memory pig

I would strongly recommend watching this keynote from this year's ISMM (International Symposium on Memory Management) on this very subject: https://www.youtube.com/watch?v=mLNFVNXbw7I

The long and short of it is that (and I'm oversimplifying the talk, of course) if you use less than 1GB of RAM per CPU core, then you're likely trading off CPU for RAM in a way that's detrimental, i.e. you're wasting a valuable resource (CPU) to save a resource (RAM) that you can't put to good use (because the amount of work you can do on a machine is determined by the first of these resources to be exhausted, so you should use them in the ratio they're provided by the hardware). Refcounting collectors and even manual memory management (unless you're using arenas almost exclusively) optimise for memory footprint at the expense of CPU. Put another way, the JVM takes advantage of the more plentiful RAM to save on the more costly CPU.