I use them and think they are fantastic. We did have a problem with leaking a little while ago, turns out it was the washing liquid i was using... It was the persil small and mighty with comfort fresh. NO mention anywhere on it that it actually had comfort in it. All my nappies went leaky!
After many many washes with daz and soap nuts, they were fine again... so, are you sure its not what you are washing them with?
I also use the insert they came with, or hemp inserts. Rarely have a problem now, unless she's pee'd more than usual, between changes.
I use both the hemp inserts at night, you know, the two that pop together. I have to say, I think the hemp inserts much better than the micro fibre that they come with, but if I change every 4-6 hours, it is fine.
I love our fuzzis. I also have some bumgenious, which are truly fab too. Can't recommend either of them highly enough.
I like the changes they've made to the fuzzis, although they seem a lot larger, and the insert doesn't go all the way from the back to the front when its on IYSWIM?
Lastly, I also fasten the legs first then the waist. Izzy is small for her age, and skinny round the waist and not big round the legs by any means, but, I still only fasten it on the 2nd from the smallest on the leg, and smallest/middle most poppers round the waist.
Are you running your fingers just inside the leg opening when fastened and making sure its all neat and flat to the leg? you know, so it is only the fleece and elastic coated in fleece which is in contact with the skin? I did find a few times, if I didn't do that, and the outer material was folded in and in contact with her thighs, then she would leak... not sure if i'm describing it very well erm... basically after i've fastened it all, I put my finger just inside the leg opening, and run it round the opening so its in contact with the nappy and her leg. Making sure its all flat, not lumpy and rucked up at all.
Sorry, i've gone on a it, I kept thinking of reasons why, and also what i do every time.
HTH