Griffin claims a 4x boost in speakerphone loudness and a max amplification of 25 dB. I did a before-and-after test in the quietest vehicle on hand in the Car Tech garage, the 2012 Toyota Plug-in Prius. Measurements were taken using a second phone running the Smart Tools app for Android's Sound Meter function. The bare iPhone 4S output a measured average of 56 dB. When we placed the phone in Griffin AirCurve, the measured loudness jumped to 68 dB. So the AirCurve doesn't exactly make its 25 dB loudness boost claim, but to my ear it's still substantially louder. Griffin's not just selling snake oil here -- the AirCurve really works.
The plastic arm's ball joint is simply pushed into the dock's socket after unboxing and gives a fairly good level of adjustment and rotation at that single point of articulation. Where most mounting arms for windshield mount kits have a suction cup of some sort, Griffin's AirCurve features a flat clip that's meant to work with either the dashboard mounting base or the very odd windshield cling base.
The dashboard base is simple; its underside is covered with a strong, permanent adhesive tape that can be pressed into the dashboard. The AirCurve's clip is then slid into the base. You'll have to leave the base in the vehicle when removing the AirCurve for storage, limiting its multivehicle use dramatically.
As I just mentioned, the windshield cling mount is, well, odd. It's essentially a plastic clip that's identical to the dashboard clip, but rather than using a permanent adhesive, it attaches to the phone's windshield with a temporary clingy material that's a bit like a large, square screen protector. Griffin says that this mount has been rated to hold up to 30 pounds, so it should be more than good enough to keep an iPhone in place. I also like that this mostly transparent mount doesn't really obstruct the view out of the windshield any more than it absolutely must. However, it can be difficult to adjust and fine-tune once you have it in place. Additionally, intervehicle transporting is difficult without picking up dirt and dust on the sticky side on the way -- you'll likely just want to set it and leave it in place.
With an MSRP of $39.99, the AirCurve Windshield Mount may seem a bit pricey for what's basically a plastic cradle with no internals. For that price, I'd have liked to see an actual suction-cup mount, and not a, frankly, cheap-feeling cling mount. Aside from that, this is not a bad car kit. There's no Bluetooth to pair, no additional cables to wrangle, just simple, over-100-year-old tech that greatly increases the visibility and audibility of your iPhone 4 or 4S without adding further complication.