I was curious if anyone has used flatwire on the outside of a wall and painted over. I have seen a few websites advertising this but was curious if anyone has used this as an alternative to in-wall wiring. I don't really want to have to go into the wall if I don't have to for my surrounds. I would love to hear from those who have used flatwire themselves.

I used flat wire a couple of years ago at a friends house.

It works well, but a few of tips

Take your time
Where possible run along trim - baseboards, doorframes etc, this helps hide it, as opposed to running it in the middle of a flat wall
It works well under carpet
use mesh tape and joint compound over the flatwire on sheetrock
BE VERY CAREFULL when sanding the compound, sand through the wires insulation and you could have a problem
Take your time, did I say that already

The end result was very good, but I am not so sure that I saved any time vs. running the surround speaker wires through the attic, basement, under/behind baseboards.

Hope this helps.