Not too closely guarded anymore. The 720 does not have an internal battery, but it does have a reboot protection circuit to guard against jiggling DC cord, dirty power, etc. This is basically a tiny 10 second battery, but not a battery in the traditional sense. I know some folks want an internal battery - but this would require everyone to pay an additional $100 for their iFly, and the weight of the unit would double, and dimensions would increase. So we're sticking with the no-internal-battery model; it's very easy to attach a battery if needed.
The 720 has a brighter screen, more appropriate for those in bright sun and a bubble canopy. It also has wifi capability, so you can interface with other devices such as the SkyRadar wirelessly, and it can perform software and data updates without having to download & move files around...just connect it to a wifi network and touch the Update button. Also it has a faster processor and more memory - these features have no immediate benefit but will enable the 720 to have some features that might not be possible on the 700 - such as 3D terrain mode. Right now the 720 is being sold only to beta users - the hardware is fully flushed out and production ready, but we have some software tweaks for auto update and a few other things. Hope this helps.
Thanks,
Walter