I use Little Lamb fitted in bamboo and cotton, BumGenius V3s, and bamboo terry flats. All the LLs were pre-loved, which I like because a) they had been washed many times and were already at the maximum absorbancy b) they were cheap and c) I like to recycle. The BumGenius were new; I got them because I was thinking to the future and thought a few birth to potty would be a good investment (the LLs are size 1 and go to 20lb, which for Adam is probably going to be approx 9 months old), plus they are more convenient for putting him in when changing away from home because once the insert is in they are like an all in one. The flats - I just wanted to try them and actually I love them because they were really cheap, I enjoy putting them on and they wash lovely - I might even buy a few more for when he's grown out of the LLs.
I am also going to try the Pop In, but I am getting really annoyed because I ordered one from an eBay shop and it never arrived and they never replied to my emails, so after 2.5 weeks I started a dispute and they refunded me immediately. Then I ordered one direct from Close Parent, a week ago, and it's never arrived either. Am wishing I'd just gone to Waitrose.
For my future stash I'm planning to get some size 2 bamboo LLs and wraps, try a BumGenius AIO and if the Pop In works, a couple more of those.