Ok... I have done a bit of research on this myself... mostly on the web.. and have found some inconsistencies... but here is a quick run down:
-LifeSpan: = 1000-1500 Recharge cycles
-Hi Current Applications
-Needs full (not complete) discharge/recharge cycyles to have maximum lifespan (to avoid Memory effect)
-Lowest Capacity (typical AA's up to 1200 + Mah)
-LifeSpan: = 500 + Recharge Cycles
-Handles partial charges and recharges from partially discharged batteries better than NiCd's (Less Memory effect)
-Becoming much less expensive
-Better Capacity than NiCds (up to 2200 or more Mah for AA's)
-LifeSpan: = About 2 years Typical.. the lifespan for Li-Ion batteries is not based on the number of cycles... but instead on the chemistry of the battery. I have not checked no this lately.. .and it may be getting better.
-Little or no Memory effect
-Does not conform to normal battery sizes.. therefore .. you cannot change from NiCd's or NiMh batteries to Li-Ion without a lot of work. NiCd's and NiMh come in 1.2V cells where as Li-Ion come in 3V Cells.
I have compiled a good bit of information on the subject.. though much is out of date and may be inaccurate. You can check it out at:http://www.qsl.net/ac4fd/
Follow the link for Battery Information