Well, here's a story for you, and hopefully it'll help you avoid a similar situation. I have an unlimited data plan with AT&T, so I always enable "download new purchases over cellular". An app here, a new album there, it doesn't impact that much. I've had iTunes Match since last year when it became available, but have never used it on my iPhone because it didn't have genius. That was fixed in iOS 5.1 but I wasn't aware, so I turned it on in iOS 6 to check to see if they added it back (they did). However, the way iTunes Match seems to work now is that it doesn't keep the music on your phone, it deletes it all. So I went in and told it to redownload all my music from the cloud. No big deal, I thought. I set it on and went to bed, on wifi. I woke up the next morning and went to class, not realizing it was FAR from done, and also not realizing that "download new purchases over cellular" becomes "download new purchases AND iTunes Match data over cellular" when match is enabled. A couple hours later, my phone was nearly dead, and I had a text message from AT&T saying I was nearing 5gb and would be throttled. My phone downloaded 3.5 GB of music in a couple hours before I caught it (and shortly after its battery died). Combined with my activity from earlier in the month, I was well over 5 GB, and am now being throttled (I can also confirm that throttling on LTE is just as slow as throttling on 3G...about .11mbps). I've NEVER even come close to my cap before, so this was shocking. Luckily, tomorrow is the last day of my billing period, and I have wifi most everywhere on campus (it's ironic that, since it was a new phone, I hadn't set it up for the schools wifi yet, otherwise this would have been avoided). I ended up coming out ok, but this kind of thing could happen to someone else, who is either early into their billing period or not on an unlimited plan, so I thought I'd warn you all...watch what options you enable!