Vinegar as a household cleaner? I would like to be more environmentally friendly?

My friend who is a clean freak uses it on everything from countertops to floors to windows and mirrors. I figure if she uses it, it must work well. Can I use it in the bathroom? Do I have to dilute it (and if so by how much?) Will it really give me a "streak free clean" on windows etc.? Any other environmentally friendly cleaning tips would be appreciated.