The mophie juice pack helium is an all new, all lighter and thinner battery charging case for the lighter and thinner iPhone 5. It features a 1500mAh, barely more than the iPhone 5's built-in 1440mAh battery, and when translated into external battery pack terms, that packs roughly an 80% refill charge.
The design of the mophie juice pack helium is similar to previous generation juice packs, though longer and even more svelte. Like Apple, mophie has made a conscious choice to emphasize extreme thinness and lightness over everything else. (mophie does, however, make a juice pack air that provides more battery.)
As you'd expect, cut-outs leave all buttons accessible, though ports are a different story. Since Apple relocated the 3.5mm headphone jack to the bottom, and that's where mophie packs much of its battery extension, they've had to figure out a work around. That comes in the form of a small extender that feels through a long hole in the juice pack and plugs into the 3.5mm port on the iPhone 5. You then plug your headphones into the extender.
Likewise, the Lightning port is covered, as 30-pin Dock connector was in prior mophie juice packs, and you have no access to it. Instead, also as before, you have a micro-USB port that charges the mophie and the iPhone 5 both. personally, I'd still prefer a Lightning port pass through. It's far more flexible than USB, and any iPhone owner will already have cables for it.
As it stands the USB port can't be used for more more than charging. None of the Lightning adapters work with it, obviously, so you have to take the mophie off to use, for example, the HDMI adapter. Also, you can't sync over USB to iTunes with the mophie on. You have to use Wi-Fi sync to connect to iTunes.
I don't sync with iTunes, wired or wireless, anymore (I have iCloud, I'm fine), and Wi-Fi sync works great, but for those who like to move large files around old school style, that'll be an annoyance.
The exterior of the mophie juice pack helium is covered in a soft-touch finish that feels even softer to the touch than previous models. Velvety even. It comes in two colors, the dark gray, which is available now, and the light gray, which ships next month.
The bottom section comes off like a cap, like with later versions of the juice packs for the iPhone 4 and iPhone 4S, and the top slides off.
There's the usual button on the back that will illuminate one of four lights to show you the current remaining charge level. In my nearly constant use over the last week and half, the indicator was accurate and the recharge consistently brought my iPhone back from the brink roughly 80%.
The mophie juice pack air is an interesting compromise, much like the iPhone 5 itself. While lighter and thinner than any juice pack before it, because the iPhone 5 is so much lighter than any iPhone, the net different is still appreciable -- an iPhone 5 in a juice pack helium feels solid.
If traveling light but staying charged is your number one priority, the mophie juice pack helium is just about perfect. If you're willing to sacrifice weight for more charging power, check out the juice pack air instead.