For appropriate levels of paranoia and/or "I'm doing this right just because", I'd hesitate a little about choosing OS X or Windows as an OS. Once you've allowed them to connect to the internet, they both do a surprising amount of "phoning home", and who knows what "the mothership" is capable of being coerced into making them do.
I'd lean much more strongly towards Linux or even one of the various BSDs if I were doing this. I'm not about to audit all of the Linux/OpenBSD code myself – but I'd feel somewhat more comfortable with them knowing the code is at least available for me to review and that there's a much smaller chance of the NSA or FBI being able to "lean on" enough people to be able to keep backdoors undisclosed.
(Having said that, if you've got a "spare" Mac and are comfortable with OS X, you'd almost certainly be able to set up a system that's "secure enough against ubiquitous recording-of-all-traffic" surveillance, and if the NSA chooses to target you specifically, you've probably got to admit your privacy battle is lost from the start…)
I'd lean much more strongly towards Linux or even one of the various BSDs if I were doing this. I'm not about to audit all of the Linux/OpenBSD code myself – but I'd feel somewhat more comfortable with them knowing the code is at least available for me to review and that there's a much smaller chance of the NSA or FBI being able to "lean on" enough people to be able to keep backdoors undisclosed.
(Having said that, if you've got a "spare" Mac and are comfortable with OS X, you'd almost certainly be able to set up a system that's "secure enough against ubiquitous recording-of-all-traffic" surveillance, and if the NSA chooses to target you specifically, you've probably got to admit your privacy battle is lost from the start…)