[legion]

Li-Ion batteries are extremely tolerant compared to other technologies. They deal with partial discharges well and can take many more charge/discharge cycles than other batteries widely available. They are also relatively expensive and heavy, and like other batteries, do decline over time (though at a slower rate). They tend to fail rather quickly once they are spent. They will also last 3-5 years.

The above is my personal observation based on the fact that I have owned a laptop since they were first available (my first was a 386 with Ni-Cad batteries) and have used just about every battery technology and have run several laptops into the ground.