I often train alone, but I have access to a good power rack, so I don't worry.
If I didn't have a good power rack, I'd probably do dumbbell bench instead, and go for higher rep sets in the back squat.
I've always trained alone. I even bench alone, though sometimes I'll give someone a heads-up that I'm about to go for a heavy weight.
Nothing like that "either you get this or you're dead" feeling to drive you through a rep.
I always train alone. Just me and this shitty rack. Set your safeties correctly, take plenty of rest between sets, and you'll be fine. Don't do anything stupid like go for heavy singles; there isn't anyone to impress anyway, and if you're at the point where singles are actually useful, you'd be better off finding a gym.
If someone uses good technique, the bar should never be over their face when the elbows are not locked out. If you miss a rep, the worst thing that will happen is the bar hitting your chest. If you don't have clips on, then you can dump the weight.
The reason I always use a spotter is to lift more weight. A lot of gym benches don't have adjustable hooks, so I burn a lot of energy trying to press the weight out of the rack. Having a liftoff is nice, and it is legal in competition... so why not use it? If I go solo, I move to the power rack and set the hooks pretty high. This makes it easier to get the weight into "benching" position.
I know some people use crappy technique, racking and unracking the bar with bent elbows, and pressing the bar over the top of their chest (BB style), but it is probably best to yell at those people and get them in the habit of lifting correctly. We do the same thing with squats, harping on good form, and we should do the same thing with bench.