>>I just purchased a GB mini and am totally amazed at the quality and usefulness of this tool.
Are there any opinions as to how it may rate as a survival tool?<<
I've become quite partial to mine. All of the cautions are worthwhile, I guess (though past generations of Boy Scouts are sniggering at us), and it's certainly worth taking the time to become very familiar with it's use.
If I think there's a fair chance that I might need to use a hatchet, I'll take the Gransfors Wildlife instead... but, like my PSK and Palm (Pilot), the Mini is useful for the very reason that it's light enough to have with me when I DON'T expect to need it.. say, for a hike in a state park where I'd better have a pretty convincing reason to even consider chopping something.
For those who have not actually held one, I should warn you that most people's first reaction to the Mini is "what's this toy?". It is very tiny indeed, and you usually need to work with one a bit to prove to yourself that it works at all.
Here in the too-PC-for-words East, I find that I get MUCH less negative reaction from somebody spotting this tiny hatchet than I would from a large (or even just a not-tiny) knife, even though the Mini would be far from useless as a weapon if it came to that. Carrying the Mini, I find I'm comfortable carrying a smaller knife than I would be otherwise, in the same circumstances, and that all works out very well here.
If you get used to using it like an ulu, it can be very versatile indeed for chopping or even slicing tasks. The shape of the blade and handle is very conducive to "choking up" on it for fine work- something not true of some other designs.
Some argue for the even lighter weight of folding aluminum saws, and it's true that they can cut through a branch faster and easier for less weight... but, as a survival tool, a saw is MUCH less versatile.
I also have one of the harder-to-find Vaughn Sub-Zero hatchets that's about the same size, and even lighter, but the handle is just so thin on that one that I don't have the faith in it that I do the Mini.
In short, there are certainly a lot better tools to have if you know you're going to be chopping wood... but the Mini is light enough to forget on your belt, and a universe better than not having one at all.