We use the gro via ai2 covers, but I generally do not use the inserts that they come with except at night with one of their boosters. My problem with them is that the poop nearly never stays on just the insert, and my son poops multiple times a day. Also, I seem to always forget to unsnap the insert. The other problem is that my son has almost outgrown them. He is 6 mo and 23 lbs. We are already on the biggest size, and it's fairly snug.
On the other hand, these covers are well made, and while my son has blowouts in disposables, and all the other cloth I've tried, he has never had one in the gro via shell. It works great with prefolds. They also have a great fit ( I actually think they fit better w a pre fold). Overall I am very happy with them! Hope that helps:)