The only NiMh packs I use are the receiver batts in my Baja's. Everything else is powered by LiPo.
I just picked up a LiFe pack for my 4PK and a new charger with the capability to charge it. Sadly my Checkpoint TC-1030 chargers will not charge LiFe/A123 packs.
There is a LiFe receiver pack available for the Baja and it's just a matter of time before I convert and be NiMh free at last.
edit: Just sold my old MRC 989 charger so I picked up a LiFe receiver pack for the Baja to try out.