My 3 yr old son has been wearing the G4 for two weeks, and we've had quite a few issues. Our first two sensors just didn't work, and our third one worked but it took four days to become accurate. However, our fourth and latest one has been working quite well (knock on wood).
In general, I have noticed that our G4 works better with more calibrations than the 7+, especially on the first day.
I have been having a lot of discussions with Dexcom about calibrations, and here's what I have been told so far. However, they admit they need more data to make actual recommendations (and they only have data in 18+ year old people who wear it on their abdomen to boot):
1. Don't calibrate on one arrow up/down or double arrow up/down. (We never did anyway.)
2. On first day, calibrate on a low BG and a high BG. (That's easy with a 3 year old.)
3. On first day, calibrate more than two times. (We've now been calibrating about 6 times on the first day, where on the 7+ we would only do 3-4 on the first day.)
4. If get a bad reading after first day, do 2-3 calibrations 15 minutes apart to get it back on track.
5. G4 can handle as many calibrations as you want to give it, as opposed to the 7+ where Dexcom suggested as few calibrations as possible.
I would love to know what other people's experience has been on the G4 so far, especially when it comes to calibrations and how to make it more accurate more quickly. Thanks.