I purchased the 820 when it was released and the rep at the store went through 3 phones to find one that didn't have a loose battery. After one day with it again the battery became loose and took it back to the store and their entire stock had loose batteries so I did a refund and bought the 822 on verizon.
Had mine now for 2 week and no loose battery issues. I am experiencing short battery life however but I think I've been hammering the phone since I've been on holiday :) ....hoping be better when I return to work and the use becomes 'normal' again.
My battery was loose and I could hear it when I shook the phone around. It never caused any actual problems for me, other than the annoyance of hearing "ker-thunk" when I moved the phone around. So I folded up a little scrap o' paper and shoved it between the side of the battery and the phone. Viola, no more problem. :)
I have the 820 as previously posted. With having time off work and having a 'new toy' I was battering it :)
Now back at work the phone is consuming around 60% only. Moderate use at work (occasional text, call, email, surf), heavy use for a good 3-4 hours after work (same stuff but more). Live tiles and pushes for a handful+ of apps. Needless to say, overall really happy.
And on thread subject, I've witnessed no loose battery at all and there is no noise/rocking.
Only thing I'm slightly disappointed with is camera flash now. Seems very weak. Faces/items near the phone get lit but flash seems useless when say trying to light up a corner of a dark room. Ar' well.