192* or 195* is stock temperature. If you live in a cold climate (such as the Northeast), or if you like to switch out t-stats seasonally for late fall/winter/early spring, stick with this.
180* is the lowest temperature you'll want to go with in most cases. I usually run a 180* in my cars out here in the desert because it gives me a little extra margin of cooling in the 115*+ summers without making it TOO cold in the winter (because it only gets down to around the 60's most winter days). Again, if you live in any kind of a cold climate at all where temps get below 50 or 40* regularly, I wouldn't advise keeping one of these installed during the cold months - swap a 192 or 195* back in there until things get back up above 60 or 70* daily.
160* is overkill and almost the same as running without a T-stat, at all ... which sucks. Your car won't get up to proper operating temperature, your gas mileage will suffer, and your engine will suffer additional wear. If you're having cooling problems, then throwing one of these in there will NOT fix the issue - it's only a band-aid to cover a more serious problem in the system somewhere, one which is likely to only get worse with time. There are very few cases I can think of where running a 160* thermostat would make sense and/or be necessary.
Oh, and go with a failsafe t-stat whenever possible. If/when they crap out, they tend to stick open, which is far preferrable to having one that stays closed and overheats your motor in a jiffy.