The Lithium-Ion battery powered tools are being very well received by both new and old users of battery powered equipment. The new Lithium-Ion powered tools have lighter batteries, hold a dormant charge longer, and offer longer on-time use than the older NiCad powered tools.
There is a substantial price-point difference between the two battery powered types of tools.
I'm still getting good service from my NiCad 19.2 volt DieHard batteries, but will eventually purchase a Lithium-Ion upgrade battery and charger kit.