OK, first let's start with a fact that Best Buy has this 3800 mAh battery case listed for $69.99 and selling it for $52.49 + tax. Is that a bargain? Nop, its a rip off because they are re-selling Chinese battery case you can buy on eBay shipped to your doorstep for $18.99 (either black or white) :
Rechargeable Backup Battery Case Stand 3800mAh for Samsung Galaxy Note 2 N7100 | eBay
Next, this case does offer an opening for s-pen, but this is a kind where I believe you have retractable usb cable to connect to your N2 micro-usb. There is another kind of similar cases where micro-usb connector is built into the case where you plug it in directly (but those cases are longer). Here you have unreliable piece of usb cable/wire that will break soon and will most likely be a thin wire that's going to offer very slow charging speed. You are looking at actual capacity of about 2400 mAh and charging speed of 700mA (versus what you get right now charging your phone at 2A speed).
It's no brainer that BB is a rip off at $53. And in my opinion, its a waste of money even for $18.99.
If you look on BB page, they also have MarketPlace listing where eForCity selling the same case for $38.69. eForCity is a famous Chinese ebay retailers, and the only reason they are not charging $20 for this case because as part of market place sale (on Best Buy, Sear, Wallmart, and others places where they have it) - they have to raise the price to compensate for 8%-10% sales fee
If you want battery backup, get one of those external batteries, I reviewed a ton in here:
http://androidforums.com/samsung-galaxy-note-2/708384-twister-reviews-accessories-gadgets.html - I personally very fond of Anker stuff. They are just like a half of dozen of other retailers re-brand HK products, but also have a very good quality control to check everything, US based and have 18-month warranty on all the products. Perhaps you might like their Slim line of Astro batteries (Slim 2 is on amazon, while I see that Slim 3 is out of stock for now).