Reporting back: I have this afternoon taken delivery of two bralet style (XS and S) and one shirt top style (S).
First impressions - when I put the first one on (shirt top) I thought I was about to be really disappointed BUT I took a minute to adjust bosoms to the right place and decided that actually they were reasonably well supported.
I also thought there would be a lot more movement - a bounce or two in front of the mirror and they're not exactly strapped down BUT again, having worn the top for a little while there's not much more movement than with a normal bra (especially since mine are getting old and the elastic is properly stretching...).
So now I'm trying the bralet - again, it's a more 'natural' shape. If you like your boobs to be held high, Wonderbra-style, this isn't the bra for you. But there's padding providing a bit of shape and support and under my clothes I don't see a difference between this and my normal bra. (I usually wear fairly plain t-shirt styles).
They're VERY comfy indeed.
I ordered an XS because I expected that's what I would fit, according to some of the reviews on the site (I'm a 32 D or DD and that's proper bra intervention sizing) but the S is better - there's more coverage and therefore more support.
I think I will probably keep at least one to give it a proper go - maybe even one of each style. I could see me wearing it with casual clothes - I'd probably be likely to stick to a 'normal' bra at work - and I reckon it would be comfy to wear in the summer when it's hot. It's the sort of thing I wanted last year (but couldn't find) when I was wearing vest tops a lot.
I will try and report back again after a few days with any further opinions/developments!