I really liked my original Boost battery case. I didn't need it a ton, since I plugged mine in at work too, as well as the car, but sometimes if I was sitting in line somewhere editing pictures or video when I was bored, or playing a game or something, that extra battery was a lifesaver. And as long as I was using a case, hey, why not have a battery in it?
For me, I've always used really slim cases that provide a moderate amount of protection without adding too much bulk. If I was willing to add a little more bulk, I'd probably consider something like a Lifeproof case. I purchased a case from Verizon when I was there, and also a case from Monoprice. I'll most likely return the one from Verizon if I end up preferring the Monoprice case. The Monoprice one does have this odd feature where it has an opening that reroutes the sound upward. I guess this means I'll no longer have to cup my phone to force the audio to come out at me.

It should also help keep any dust or lint out of the speakers.
I'm not in any rush to get an HDMI cable...just convenience thing. Once in a great while I want to plug it into something, like my 720p LED portable projector, and it would just be handy to have.
Yeah, mine was more or less for my iPad more than my phone, but it was usable on both. Getting the iPhone 5 will most likely make me sell my iPad 2 and upgrade whenever the iPad 4 comes out. That means I'll simplify things by only owning a single type of connector!
I was going to sell my last ATV2 at markup, but a local buddy was looking for one so I had pity on him I currently have no more AppleTV's in the house. Again it's like the HDMI adapter...not something I need all the time, but it's convenient to have when I do want to do something with it.
It's a bit off-topic, but I was curious about what sort of mark-ups are you seeing on the ATV2? I built a silent HTPC, and I might just sell my ATV2 since XBMC supports AirPlay. Do people prefer the ATV2 to be jailbroken prior to selling it?
I'm actually not super super excited about the upgrade to the 5. I mean, I think it's cool and all, but I'm mainly doing it for the camera (even though it's mostly the same) and because I had a family member who had an early upgrade available that I could trade my 4S to in order to get the 5 at normal price. I've taken 20 to 25,000 photos on mine so far and really just have fun with it, plus I use it for most of my little for-fun film projects and wanted to switch out from 32gb to 64gb anyway
I traded my 4S into Amazon, and I've been using my old 3GS in its stead. Let me tell you... nothing gives you an appreciation for a faster smartphone than downgrading like that! Whether it's trying to scan a barcode in the Amazon app or browsing the web, you really begin to miss how snappy your previous phone was. If the iPhone 5 can truly utilize the stressed 1.5-2x speed increase over the 4S, it will seem absolutely amazing to me given what I'm using right now. Although, on that note... I really hope I do get my phone on Friday! I don't know if I could deal with the 3GS until October. :$
Since I'm switching carriers, I'll probably try to sell my 3GS after I'm done. There will be no tears shed!