The JVM eats a chunk of memory in order to make its garbage collector more efficient. Think of it like Linux's page cache.

I haven't worked with too much Java, but I suspect that the distaste many have for it is due to its wide adoption by large organizations and the obfuscating "dressed up" tendency of the coding idioms used in large organizations.

The runtime isn't inherently slow, but maybe it's easier to write slow programs in Java.