Mine is wiggly, I thought it was just the new design, however it doesn't seem to have any inhibiting factor to the performance of my unit. That being said I am struggling with some of the other little bugs. I am sitting home and always have Full Bars and solid 3G and 100% WiFi, however with the 4 my signal goes from full bars to none, WiFi is spotty, and overall it just does not make sense because my 3GS has perFect WiFi, and I always had Solid Full 3G in my house.
I was going to get a bumper but the NJ Apple store where I bought mine was sold out. This is a striking point to my i4 experience, I think the 3GS out of the box was much more solid however I will give it a day or so for the AT&T activity to calm down before making a decision to return it, as I do not see Apple replacing it right away due to short supply.