What is the difference between the old and new. I have an old one and really can't figure it out. Is it worth getting the new one?? Will the new cup fit on the old burner??

The new stove comes with a stabilizer base that you had to buy seperately before(cool), a larger valve knob(very useful), redesigned ignitor(better, but still can be unreliable), and a temperature indicator built into the pot insulator(neat, but unnecessary). Overall a better product, and it doesn't cost any more!

Jetboil also claims that, "The newly designed burner secures the igniter, protecting it from bumps along the road." Their FluxRing is supposed to be improved as well to deliver more efficient energy transfer. This means less fuel used to boil your water. This might translate in to faster boiling times, but it would probably depend on a lot of different factors. From personal use, I boiled 16oz in about a minute and a half. Jetboil's website claims a boiling time of 2 minutes. My results though, are from a high elevation standpoint. As elevation increases, the boiling point of water decreases at a rate of 1*C per every 960 feet elevation increase. A lower boiling point would require less time and energy, assuming the fuel is at an ideal temperature.

The difference between the new Jetboil Flash and the old PCS system is that the cup has a color changing flame that lets you know when the water is hot (as if you can't tell). It also has a clear measuring cup and a see thru lid. All other cups, new and old, will fit on the system. Everything else is the same...

New flash has heat indicator on Cozy( glows red when at a full boil) , comes with a fuel stabilizer ( tripod) Burner is slightly modified