Are general purpose operating systems really that inefficient?
I've thought about "boot into JVM" before, and I think it's enticing for technologists since it's so "clean", but all the projects aiming for this seems to have died from lack of interest (e.g. BEA Virtual JVM/JRockit Virtual Edition).
Edit: Perhaps I should explain where I'm coming from. I work on a high-performance spreadsheet system. One of the things that makes spreadsheets interesting is that their computational model is powerful enough to be valuable, yet not so powerful as to amount to general-purpose computing. Think of a server that doesn't need to do anything but access spreadsheet data, perform spreadsheet calculations, and serve them over the network to some client. Such a server's responsibilities are so specialized that one can't help but wonder how far down the stack one might push them and what one might gain by doing so. I daydream about this sort of thing.