In all honesty the biggest difference between NiMH and Lipos are the weight and charge density (capacity). The voltage is slightly higher (nominal 7.4V lipo vs. 7.2V NiMH) but the best thing about Lipo is that a 4,000 mah pack will keep its voltage up better than a NiMH 4,000 mah pack and since the lipo pack weighs about 100g less the car will be faster and run a little longer longer.

There is almost no charge memory and the packs seem to keep their ooomph after many chargings. You can use one pack all day by charging it after each run. For most racing a 3,600 to 5,000mah pack is more than sufficient.

The only caveats are not to overcharge, over discharge and to balance the pack frequently. Also you should guard against punctures (hard cases make this easier).

The Tamiya TA-06 was designed for Lipo use. Not sure about the Mini and if that still needs a stick pack form factor (rounded sides).