As far as extra features go, the armband/carrying case is the most notable item (as far as armbands go, it's quite decent, and should accommodate most non-phablet smartphones). The headphone can connect with up to eight devices through Bluetooth, and also doubles as a wireless headset thanks to a built-in microphone (call quality was good).
A play and pause button, along with volume controls, sit on the left earpiece, while the power and phone buttons are located on the right side (holding down the phone button activates Siri on iPhones). Additional controls, such as the ability to skip songs or go back, can be accessed with a long press or double tap of the play button. Charging, which should take about 2.5 hours, is done through a Micro-USB port that can be accessed by lifting a small cover on the right earpiece (a USB cable is included).
Although small and lightweight, the BackBeat Fit has decent battery life -- better than the BackBeat Go 2 anyway. While listening to music, the headphone is rated to last up to 8 hours at moderate volume levels, or up to 6 hours of talk time. In standby they can last up to 14 days, while a "Deep Sleep" hibernation mode promises up to 6 months of battery life. That comes in handy should you not use the headphone for a while and suddenly decide you want to.
As for sound quality, I think most people will be pleased. For a Bluetooth headphone, the Fit sounds fairly detailed and delivers a decent amount of bass, particularly for an "open" earbud. However, that bass performance will dip in noisier environments (if you can't seal out ambient noise it will compete with your music and the bass takes the biggest hit). Also, the headphones do leak some sound.
The Fits aren't going to sound as good as some wired in-ear headphones in this price class. The Monster iSport Immersion and more expensive iSport Victory are both more dynamic and deliver bigger bass. However, those headphones are designed to be jammed into your ears.
At the end of the day, the important factors for me when listening to a wireless Bluetooth sports headphone are that the headphone doesn't sound muddy, is reasonably well balanced (the bass isn't pushed too much), and can play loud enough. The Fit easily cleared my lowered bar.
Since all our ears and heads are shaped differently, I can't guarantee that there won't be little things about the BackBeat Fit's design that bug you. Nor can I tell you how these headphones will hold up after months of intense use (I used them for two weeks). However, my impression after testing them is that they're one of the best wireless Bluetooth sports headphones available. Not only do they offer a comfortable, secure fit, but they sound decent and offer enough battery life to get you through a day.