My NB is 1 week old so thought I'd chime in with my experience so far. I tried the Jillians Drawer's trial package and knew just from playing with the diapers that AIO's would be the way for us to go. Anything with 2 pieces just seems to complicated to me, and would be harder for daycare in a few months.
I like the BumGenius Organic 1-size AIO, so I started stocking up on them used, but they will clearly not fit until he is at least 12 lbs. I'll continue to buy these as I find good deals until I have a full stash. I like that they will last for a long time and for other kids if I take care of them.
I also got some Thirsties 2.0 XS size, although I worried they would only fit for a few weeks. He ended up being long and lean (6lbs 10oz at birth, and down to 5lbs 14oz at one point) so these are pretty baggy on him and may last a while (they say 12 lbs). We started using them as soon as the meconium poop was gone, but they seem to rub his umbilical stump. We're using disposables for a couple more days until it falls off.
Overall, our few days with the Thirsties and the washing cycle went well, and DH is a big fan of them too. I hate the feeling of the disposables, the Pampers feel so fake and plasticy, and the 7th Gen are like unbleached coffee filters, I would not want them on my skin!