I just flew it on a 5S LiPo for the first time today, and all I can say is WOW!!!

Power is WAY up, weight is down by more than a pound. All the sluggishness and bad characteristics are gone. It climbs great, it turns better, approaches and landings are much easier since the weight is lower.

My recommendation would be to not waste 149 dollars on the 2 NiMh packs / charger combo, put that money towards a LiPo pack(s) and charger instead. My plan was to keep flying the NiMh packs, but really I don't see that happening after flying the LiPos.