I'm a qualified first aider as well as instructing first aid to young people and about to start instructing adults through both Hearstart Scheme and the Scouts First Response scheme.
I have completed all sorts of courses, combat first aid, HSE, peadiatric, Mountain Rescue / Wilderness and have been "doing" training for the last 18 years through the different roles I've had at work.
I am one of these sad buggers that enjoys it. I also enjoy passing on my skills to others and make sure that courses I organise or deliver have a certain degree of "realism" (Just ask the fainters I've had!!)
It matters not the amount of training you've had however until you have to actually use it. CPR rarely takes place with a slim looking streile dummy. Normally you are surrounded by wailing family members with overweight individuals, struggling to find that "notch" whilst emptying their mouth (and occassionally yours in the "old" days) of vomit and body fluid.
Try counting compressions whilst trying to instruct others to do something!
Similarly, blood gets messy and it's not at all pleseant realising that someone is dying in front of you and there is nothing you can do to help them.
I've dealt with some pretty horrendous injuries from gun shot and knife wounds to multiple RTA's and amputations and it's not even really my line of work!!
Everyone should have basic first aid training because it really could make the difference!