Battery life all depends on what your running on the tablet, I can get 6-8 hours out of it. As with anything though I always carry a spare batteries with me though for my LX-7 and other electronics so those longer days I can keep going. Sonar works just like every other digital sonar they have out, just a couple more button presses as its all touch screen. They just released an update for it as well which has improved it, haven't given it a full test yet.
Worth the money? It all depends on how you are going to us it. If you are only going to use it for the sonar and gps and none of the other functions on the tablet, to me your only utilizing 10% of what it can do. It would be hard for me to justify the purchase but Im not going to tell you how to spend your money haha. If you are a run and gun kind of guy, I would look at the LX-7 and the shuttle. If you have a wheeler/sled you can mount it on to utilize the GPS then put it back into the combo pack to use while fishing and only move 1-2 during the day, I think having the bigger screen with the functions that it has is totally worth it. Having a 9" screen to look at while walleye fishing, zoom ect... is worth its weight in gold. Not to mention, if you do have issues with anything a quick email to Marcum should get it taken care of. Never been let down the guys over there.