Many years ago, and only ever did once. I can't remember what it was for. I didn't have any particular aversion to it up until maybe the last year, there just didn't seem to be any benefit. Just paying for things with extra steps. These days like everyone else I'm concerned about the energy wasted in mining. You do you but I won't support that.
Umm... I don't think anyone has really seen it as a medium of exchange for a long time.
It's a speculation vehicle, that costs an obscene amount of power. Hopefully one day soon we'll run out of "greater fools" to buy in and it can all come to an end.
About a couple of weeks ago. Whenever possible I pay with LTC or XNO due to fees and speed, but some businesses only take BTC. The downside is that I end up spending probably a dollar or two in tx fees but still it's faster and cheaper than a money order and a postage stamp.