It all depends on what you want to do with it. Crunch numbers? No way after some point. Prepare the Air Force's annual budget submission without information leaking? A real example of a perfect fit. Or provide the IT for MIT's EECS department? Good fit, until MIT-MULTICS was shut down as part of Honeywell killing Multics and the Cambridge lab which did work on it (I played a role in moving off that).