For MOST motorcycle users, the LiFe batteries would be a huge improvement. Lead acid has a discharge curve that tapers, meaning that the less charge it has, the less power you have each time you press the starter button. You will know when the end of the charge is coming because the starter has a harder time spinning, the lights are weaker, etc. Lithium batteries have a discharge curve that is nearly flat, meaning that you will get almost the same full-power kick on the starter motor until the battery is empty. Suddenly you will simply not start. Nothing. The charge simply falls off a cliff.
The exceptions for who would benefit would be the folks who ride when temperatures are regularly less than about freezing (really about -10C) and very few people ride their bikes when it is less than freezing. It's not that the cold affects the battery function directly (generalized for motorcycle usage anyway), it's that cold charging takes the lithium out of the electrolyte and creates small deposits, shorting the anode and cathode within the cell. The shorting usually just burns holes inside the battery, killing it, but there have been thermal runaways and fires. The fires are almost never in Lithium Iron (LiFe), which is the most stable of the lithium cells.
Because this can be such a hazard, many chargers and some internal battery control circuits will prevent charging when it is freezing out. In real-life terms, this means that somebody like Snakebitten in Texas would not charge after the first starts on a few of the coldest winter mornings, and would not be aware when the battery begins to charge after enough engine or sun heat gets the battery above freezing. No problem. For somebody like Rem, living near the Arctic, he may be drawing on the battery enough to discharge the thing.
One other safety note: Overcharging any lithium is extremely hazardous so follow directions. If you want to see excitement, Youtube some videos of people overcharging lithium cells.
Charging cell phones would be no issue. Note also that the energy density of Lithium beats the heck out of lead-acid and nicad, so a small appearing Lithium probably has more energy than a much larger one of those. When you think about using a little juice to charge your phone, imagine doing it from a lead-acid at least double the physical size of the LiFe that you may be looking at charging from.
Finally, heat shortens the life of Lithium batteries, especially when stored hot. You desert dwellers would be wise to research the life others are getting out of the exact model you are interested in for YOUR area.
Good source for more info:
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
But when I replaced the stock battery with the Shorai there was room left over in the battery box for the ECU and some padding. ::008::
