As has been said, OpenSource software is, especially in terms of \"knowing what you get\" much preferrable to closed source software.
Additionally, though this won\'t help you much, I\'m pretty paranoid about downloads and the internet, but I have had no doubts about PS, ever.
Of course, I still scanned PS for viruses, and repeat after each update to .exe or .dll files, but I\'m scanning everything that has been on a computer that doesn\'t belong to me.
Needless to say, I haven\'t found anything even remotely suspicious in PS yet (if you trust the opinion of random people on a forum (me, in this case), that is).
IMO, PS is way safer than a Microtheft Windoze update.