I have had the Icon since release day too.
I am now also noticing the squishy/creaky/loose back cover.
I tried to ignore it, as it really doesn't effect the function of the phone, which, BTW I love (especially with the 8.1 update)
I have been using a case, but I really don't like to, but that's the best way to not notice the squishy/creaky/loose back cover.
I spoke with the Verizon store and they said they would swap it out with no questions asked.
I guess that's what I am going to have to do.
I guess I will have to re-install all the 8.1 updates too of course.
Hopefully the new handset won't have the same issue after a few months.
The back wasn't loose at all for the first couple months.
It seems only a few others have this issue, so it must just be a build issue not a systemic issue with the design.
Oh well, if that's the only issue I am having that's pretty good.