These compact batteries charge rapidly (although I tend to use 1c after flying), hold their charge and improve servo response over the much heavier NiCd/NiMh 4.8v packs. By switching from standard 4.8v NiMh packs to this smaller 700mAh pack I saved 75g! I still get 5 x 9min flights on my 25 size Easy Stick (see review) with 2 flights safety margin.
I also feel more confident that he 6.6v voltage (even with higher loads) will help prevent "brownouts" that can occur in 2.4gHz systems under load with a 4.8v pack.
Only downside is that like all LIFe packs, voltage isn't a good indicator of available power. Use, recharge and see mAh input to estimate average mAH use/capacity.