Certainly such big difference can't be explained by more effective system calls. I attribute this to Microsoft's superior C/C++ compiler. Back in my C++ loving days I played with various compilers regularly, and MSVC has always been the most optimizing, and kept advancing rapidly from version to version. It also compiles 2-3 times faster than GCC if I remember correctly... uhhh I miss it. :-)
Also his JRuby startup time is inaccurate. No way JVM starts in under a second: it's more like 2 full seconds on his hardware. More likely he had some of JVM in the filesystem cache. Vista/OSX will pre-fetch JVM modules even after you reboot (not sure about Linux) if you run Java software and especially if you have 8GB of RAM...