RE: Life battery's
It's not better, just a bit more voltage. As quoted above, the actual voltage the receiver sees is very close to the same between the two. The nominal voltage ratings really don't mean much with batteries. The number that actually matters is how much voltage is actually there under load from fully charged to the point where you recharge.
As stated above, the only negatives I see are that you need an LiFe capable charger and some data suggests that the LiFe's won't last quite as long as NiCd's will. But most of us replace our packs every 3 years anyway so that's a non-issue. Besides, LiFe's a generally a little cheaper than top quality NiCd's, so the lifespan issue is a wash.