The data about injuries in non-union states brought up a point I forgot to make.
A lot of people joke about how someone in a union isn't allowed to change a lightbulb if they aren't in the Electrical Worker's union, or something along those lines. It's a little extreme, but there's a good reason for this: most union contracts specify that you have to be trained to do a task before you're allowed to do it. Quite a lot of this training, in manual-labor type jobs, is about safety equipment and safe operating procedures. Similarly, one of the things that unions will bargain hardest to keep or improve are safety conditions, the availability of safety equipment, and the right to refuse to do a task if you're not trained in it.
Sure, it seems silly when someone won't replace a 60W incandescent bulb in a desk lamp. It's a lot less silly when you're asked to replace 4 foot fluorescents in drop ceiling fixtures twenty feet high.
Similarly, another favorite tactic of employers who want to 'get rid of someone' (and fuck them over on Unemployment) is to assign them tasks that they're not trained for and then can them when they fuck up. Or assign them tasks that they know are unsafe, wanting the employee to refuse to do so. Another one is to fuck with your schedule so that you wind up working different shifts on a few hours' notice, or closing/opening shifts on concurrent days -- sometimes for weeks -- and never, ever give you a set schedule so that you can actually plan your life and take care of things.
As for other's experiences with union jobs ... counting only the jobs that could feasibly be covered by a union, on the non-union jobs I could never count on how many hours and how much pay I'd make each week, I could never count on having a particular day off past that week plus maybe a few days, and never, ever even got unpaid sick leave that wasn't a strike against you. I've also been fired for doing something wrong for like four months in a row -- basically, since I was given the task -- yet no one in that time ever told me that I was screwing it up, and there was nothing to refer to so that I could find out more about it. In the union job I've had, I had a regular schedule, 40 hours/week every week, paid vacation time, and paid sick time. All of the rules and duties of the jobs were laid out in print, and there were procedures in place to ensure and record that every employee received a copy of them every year. Except for the most newly-instituted procedures, there were extensive manuals and support documents, training aids, all that stuff. Oh, and my work was reviewed regularly and I was made aware of the results of those reviews in a timely fashion.
I've also seen the difference between union and non-union supermarkets in my area. I've noticed one subtle but extremely important difference: the employees at the union supermarkets generally don't seem unhappy to be there. The employees are more diligent and significantly more professional. The morale's much better, and as such, I get better service.