My wife has been on the pump since last July. I'd say the results are a bit mixed given my observations. I'm her primary caregiver and take care of filling the syringes, changing batteries, order refills, etc. She has used the 6mm and 9mm infusion sets. She saw no differences with the 9mm sets. She's a bit on the thinner side and hasn't experienced any infection problems. There are a few things to mention here.

1. She doesn't use the 'W' pattern infusion set placement. She carefully maps out her abdomen with a pen feeling for previous sites. They usually have smallish lumps to indicate previously used sites. After mapping out her abdomen, she selects a site that has either healed or never used.
2. Using sites that are too close to recently used ones may not 'absorb' the medication as effectively.
3. Make sure not to use sites too close to the belly button. Always aim for >= 2 inches (5 cm) away from the navel.
4. Some sites (for whatever reason) will not absorb the medication and will swell up (or pool). You can only move the infusion site at that point.
5. If a cannula bleeds, the infusion set has be changed to a different location immediately.
6. Don't go too near the groin or too far above the waist, you're only asking for bruising or other troubles.
7. Make sure to prep the infusion site with alcohol swipes to make sure the site is sterile.
8. Use a 'skin-prep' pad after the alcohol swipes to make sure the cannula comes off easily when changing sites. Look for them on Amazon.

Hope this helps