Physically, the Boost is about the size and shape of a deck of cards, or a medium-sized phone; either way, it's a little smaller than your iPhone. On one end you'll find the standard 30-pin iPod connector retracted into the body alongside a white LED that can be enabled as a flashlight (more on that in a bit). On the other end is a small keyring, though we're not too sure why they bothered -- we can't imagine trying to put this thing on an actual keychain because it'd get scratched up pretty badly and it's simply way too big to be carried that way. One side features the micro-USB port for charging. On the top, you've got the slider for extending and retracting the 30-pin connector, and the bottom has a button that lights up a bar graph of four white LEDs showing the Boost's current battery level -- a hat-tip to the battery indicator on MacBooks. Pressing and holding the button will enable the LED flashlight on the end; its level of illumination is about what you'd expect
A strip of soft-touch plastic down the middle of the Boost makes it comfortable to hold in the hand without losing grip, but unfortunately, our design praise ends there. Apart from the soft-touch, everything about the product feels extremely cheap, from the metal-look plastic endcaps to the flimsy shell that feels like it could crack if you applied just a little too much pressure. All visible parts of the Boost seem to be exceptionally susceptible to scratching and wear -- as evidenced from some of our pictures -- but this is the kind of product that you'd want to be able to throw anywhere and carry with you without having to think about it, so that's a bit of a problem. Our biggest beef, though, was with the slider used to extend and retract the 30-pin connector: in a word, it's awful. It seems like the intention is to press down on the slider to "unlock" the connector and allow you to move it back and forth, but it frequently gets stuck, requiring additional pressure. Spraying a little WD-40 in the moving parts might work wonders, but we were too scared to try. Even once you get the connector extended, though, it's not long enough to comfortably maintain a connection with an iPhone 4 in a bumper -- you can do it, but just barely -- and either way, there's no way to use the phone while it's charging because the Boost dangles perilously off the bottom. A smarter design would've been a retracting 30-pin cable, or alternatively, just a USB port and a bundled 30-pin cable that we could connect to it; that'd make it far more versatile, anyway.
Performance, however, was a better story in some respects. The Boost charges your phone quite rapidly -- making both the phone and itself quite warm in the process, but not alarmingly so. Connected to an iMac, we were seeing a charge rate on our iPhone 4 of roughly 1.08 percent per minute; by contrast, the Boost put down 1.2 percent per minute, or about 11 percent faster. The only bummer is that the Boost won't top you off if you're low; we averaged about 54 percent of a jump in our iPhone's battery from a fully-charged Boost before it went dry. Certainly enough in an emergency, but not a battery doubler.
We love that Boost is trying to solve the iPhone's battery dilemma -- we just came away thoroughly unconvinced that this is the product to properly solve it. Mophie's own Juice Pack Air for the iPhone 4 is in many ways a superior product, but if you insist on keeping your reserve battery as an entirely separate pack, we wouldn't hesitate to recommend even the USB-equipped Juice Pack Powerstation
over this. To Mophie's credit, we're quite certain they didn't know of the iPhone 4's bumper situation while the product was under development... but that doesn't mean users should feel alright about buying a battery pack that isn't optimized for their phone. Our guess is that we'll see a new generation of Juice Packs before too long -- and until then, the Boost is a pass.