To the XCAPEPOD!
I usually go 200 plus miles on the first half. That's how I know whether the tank will be a good MPG tank or not. I've also driven 125+ miles on the first bar. Now, if all the bars lasted that long...Perhaps. I've filled up three times since and it's registered full. But I have noticed that it's saying I can go about 200 miles on half a tank. I typically average 300 miles a tank, so I'm not sure all the bugs have been worked out yet.
Gas gauges in every vehicle I've ever owned were not linear. I'm not sure why it can't be done, but no manufacturer (of an affordable vehicle anyway), seems to be able to do it, so I don't worry about it. Mine does the 7/8 thing as well, but so did my previous Nissan truck with an analog gauge. No big deal. As someone else said, as long as the empty side works, it's nothing to get worked up about, IMHO.
The cure for the common cold and a linear gas gauge will elude humanity forever.