It makes you think.
Well, more, it makes you shit scared!
As usual one's assessment of risk is skewed by the most recent experience.
Even so, I do think that the potential life saving benefit of a defibrillator way out weights the cost. More to the point, I can afford the cost. I can't afford to drop dead (IMHO).
We took advice from Red Cross, and we now have one at the office, and I have one at home too. I am surprised more offices do not have one. Our first aiders at work are trained on it as well (thanks to Red Cross), but it is pretty idiot proof.
I hope we never have to use it, either of them.
P.S. From the comments, one thing is getting one that can go outside, and so be accessible to others (e.g. others in my road) if needed. The ones we have are not for outside installation, sorry, but certainly something to consider if you are getting one installed.