The unit I have is (http://www.powerstationusa.com/brands/Powerstation/product.php?mod=PSX3) (no affiliation). It looks like I was mistaken and the manufacturer is still making them, I just can't find them for less than $100 at Costco any more.

They're surprisingly versatile.

Unlike smaller units, they have a good shot at successfully starting a car with a totally flat battery. They have a USB port, and 12VDC ports that can with an adapter (kept in each car) make more USB power. They both have air compressors and little area lights on them as well. I can run a ham radio HT ("handy-talkie") for at least a week, and a more powerful radio for at least 12 hours of heavy operation.

If I'm providing any sort of IT support at a CERT callout, I can power a laptop with it for a while.

While all three cars have jumper cables, it's much faster and easier to use the jumpstarter, and I think it's a bit safer too, being much harder to accidentally short a 12VDC system.