Preach on! :) Yes, we think we're better/more convenient than walkie-talkies for a few reasons.
1) We integrate with the smartphone you already have on you. 2) The asynchronous communication, as you said, allows for less miscommunication. Plus, with delivery confirmation receipts you KNOW it didn't just disappear into the void somewhere, and was actually received by your intended recipient(s).
3) You can direct the message specifically to discrete individuals or groups. You don't need to worry about being on the same channel or hear other people you don't know yakking.
4) You can share your ___location on detailed offline maps.
I hear you, but I'd bet on my MURS capable radio to outlast my iPhone (with BT on) and whatever spare (heavy) batteries on my week long backpacking trip.
Maybe not the use-case you guys are targeting, just food for thought.
Either way, great idea/product and use of the Multi Use spectrum.
The app comes with a vector map of the entire world. You can then download specific areas to get complete detail (i.e. down to hiking trails and city blocks) before you head out -- depending which maps you want you'll download via small country (e.g. France) or state (e.g. California). All goTenna maps are free!