I have one which I've used a few times. Seems pretty good.
I need bigger nappies for DD and I'm torn between these and bumgenius. BG seem more convenient, but I like the fact that the MB ones are bamboo instead of synthetic fibres.
I'm wondering also how long each will last. I reckon the BG will last til potty training but the MB don't seem to have as much room.
Also the MB seem more of a faff to assemble especially as I'm using a fleece liner. I suppose we'd get used to it in the long term.
Any pop-in users out there? What do you think of them?