First impressions are:
* it's very light and definitely smaller than the Mini 10, which is the other instax that I have.
* it does however look lovely - I think the trim will get scuffed quite quickly, being plastic, but for the moment it is great. It doesn't look like a kids' toy like the other Instaxes. I've heard a lot of people say they've been put off by that look.
* it is quiet - none of the grinding in and out of the Mini 10 lens.
* the bulb mode still doesn't make it very useful for night photography. The lens is still f12 or so and even though Instax film is ISO 800, you don't get a huge amount from 10 seconds or so. It could be okay for reasonably lit night scenes though.
* function buttons seem reasonable, but the "mode" thing is not very self explanatory - I'd like to know precisely what the modes do. I think "party" is fill flash. I'm expecting a bit too much from the "manuals" (vague pieces of paper in fifty languages) there, I may have to just experiment.
* macro capability (up to 0.3m) is more useful than one might have thought, because the lens is so wide that you need to be arms length or less to take a portrait, and previous models only went down to 0.6m. NB focusing is now "macro", "normal" and "landscape" rather than previous ones - not sure precisely which ranges these are supposed to cover.
* pictures are... Well, like any other Instax. Very sharp but tiny. Instax film has always seemed pretty good to me.
I haven't had any occasion to really take pictures with it and I don't want to just snap them off at anything, but will try taking it to work and getting some shots of the canal and people on the street.
It's definitely an improvement on the Mini 10, and hopefully will sell well as it addresses the "omg I am not taking that out in public I am a grown-up" issue, but whether it's worth upgrading if you already have one... maybe not unless you really use it a lot.