I think I'd have to agree that the Instax color films are very good, but all the Fuji Instax cameras have varying levels of suck (and so far I'm not terribly impressed with the monochrome film, but that might just be my camera -- see below).
The Lomography ones don't appear to be a step up, and no one makes a really accessible/affordable Instax back to fit, say, a Graflok (there might be film positioning issues there; all the hacked setups I've seen for the RB67 bypassed the rotating back and went straight to the body, or built onto a P adapter that does the same).
B&H had the Mint-built Rolleiflex Instax on sale last week for under $500; it's normally $700-ish. For my money, if I had it to spend, I'd get the Mint folder -- but it's $700+ and fully automatic -- though at least it has a decent lens.
Apparently it's not too difficult to hack a lens and shutter off an old folder onto an Instax body, and in that case you can use the cheapest body you can find for the film size you want (since all you actually need is the film holder and processor, plus the light tight chamber). I've got a Mini 9 that I bought with this more or less in mind (that, or hacking it to attach to my RB67).