Yes, that was my point #2.
The only real need for a spotter is for barbell bench pressing
I was specifically thinking about the bench-press-like machine press, but also true for the dumbell fly exercise.
I do the free-weight lifts, just not with heavy weight. When I want to seriously stress my muscles I go to the machines.
I just started with the bosu-ball stuff last year and I have to say I like it. It hits stabilizers the squat doesn't begin to touch. I'm a sailor- just got back from a week-long bareboat charter in pretty choppy seas, and I really like the results. I'm not sure I can articulate it though- while it helped my balance, it also helped my strength while maintaining balance. For example, the task of picking up a mooring ball with the boat bouncing seemed easier. But that may just be a distorted perception.
It's a bit like barefoot running vs shod running. Shoes protect your feet, so they are ostensibly safer. But they also make it easy to have bad technique and wreck your joints, especially your knees.
> (1) If I'm doing a chest exercise, for example, with 270+ pounds, and I fail on a machine, I can get out of it. With free weights, I need a spotter and it's much trickier.
Depends on what you are doing, and how you are doing it. The only real need for a spotter is for barbell bench pressing. There you can bench press in a squat rack with the safeties set to the right level. But there are lots of other exercises that provide a similar benefit without trapping you. E.g. (weighted) dips (on rings), push up variations, hand stand push ups, standing overhead presses.