I've been qualified for the first aid at work course (three day course) for about 6 years now and it's great, thankfully I've never had to use it at work, but I've had to use the training in a few other instances in civvy street as it were, it's definitely worth doing, even if only for piece of mind.
A good example was at the Big Bike Bash this year where a 7 or 8yo boy had been smashed in the face by another kid dancing around in front of him with a bike hat on, totally accidental of course, but this kid was screaming and covered in blood, his dad looked mortified and generally people were looking at them going "f*cking hell!" No one was really helping out even when he asked for a first aider, I was queueing for beer, saw what was happening and went over. All it took was a couple of beer towels and some reassurance and the boy and his dad were ok(thinking about it the dad looked like he was sh*tting it more than his son!), not sure how he explained it to his wife/the boy's mother though!
Being in the right place at the right time knowing what the right thing to do is worth it's weight in gold, especially when it could potentially save someone's life.