I've used Nano's - I keep a few "in stock".
The good:
I like that I can pop em on my 510's, which I still use, or on an Ego, etc... Got some cones so it looks kinda cool too.
Easy to fill, very little trouble with leaks, etc.
When they're working right, I like the draw, and the flavor, etc.
The bad:
They won't last all day (but you could carry a couple filled...)
About 1 out of 3, in my experience, have a NASTY chemical/plastic taste that lasts sometimes a few puffs, sometimes the whole first fill-up
I don't get a lot of fills before they seem shot - burnt taste, despite careful use. You have to consider these as disposable.
I like "mini's" - this is the only "skinny one" I've used if that's what you want, but I've also got:
Mini Vivi Nova, Mini T3, and EVOD - all worth a try (leaning towards EVOD as my fave).