It's an FM radio receiver like the one in some other HTC models... Jut for listening to the radio.

I've never seen a phone that broadcasts FM, The problem is that this wouldn't be very practical since it'd kill the battery in minutes.... If you want something like that you can buy a battery powered accessories to does it.

I'm just back from the store and everything worked great!

I knew the update would wipe the phone, so I backed everything up and then headed to the store, I arrived 10 minutes before my appointment, the store was packed, but they took care of my phone right away.
They were very pleased to find I had backed up my contacts and told me it shouldn't take long, I left my phone and went to grab a bite and when I came back, about an hour later, the phone was ready and working great!
I'll try to post some of the changes I have noticed with the phone, but the service at the Sprint store was great and my Samsung Moment is rocking the latest version, is great that Sprint rolled this out fast at least for us geeks that couldn't wait.

My recommendation: Call in advance and make and appointment, or if you're sure of a store that's already updating (like Overland Park, KS) you can schedule your appointment online!

You're right Rene, my Bad!

But it's fixed now, thanks for your observations.
Just to clear it out a little bit though, figures are worldwide, but it's undeniable that US events affected the chart a lot, hence my remarks about it; hope they have a little bit more context now.

I'm sorry @prupertplum but this update is exclusive for Sprint costumers in the US and it's probably going to be rolled out OTA, so you'll have to wait for an official European Hero update from HTC. :-(