The U5 includes menu options for music, FM radio, Fitness, voice recorder, and Datacasts (podcasts pulled over from Samsung's PC-only EmoDio software, included with the U5). You won't find photo or video support on the U5, but that just comes with the territory when you're dealing with players in this size and price range.
The U5's music player is surprisingly well-appointed for a $40 MP3 player. Songs can be browsed by folder or ID3 sort (album, genre, artist) and format support extends to MP3, WMA, Ogg, and FLAC. Noticeably missing from the supported format list are AAC (for all those iTunes downloads) and Audible audiobooks. If having both AAC and Audible on your MP3 player is critical, you'll need to look at an iPod, Zune, or Creative Zen. Otherwise, a fitness-minded MP3 player like the Sony W-Series will at least afford you AAC support, and the Sansa Clip is your best bet for an affordable, gym-ready, Audible player.
The U5's FM radio supports automatic and manual presets, and also includes an FM-recording function (recordings are made as 128Kbps stereo MP3). We were happy with the quality of the voice recorder, which captured clean, 128Kbps mono MP3 recordings without the high-pitched whine we often hear with these devices.
The U5's fitness application is undeniably its most unique feature, allowing users to enter in their weights and fitness goals, and track their progress using a workout timer. It's a far cry from the sophisticated, pedometer-based Nike+iPod system, but at $40, the U5's straightforward fitness utility makes for a decent workout companion. While fitness mode is engaged, animated characters (remember those Popcon guys from the Design section) appear onscreen to run and sweat along with you. When you're done, a performance screen shows you an estimate of the calories you've burned and the length of your workout.
From an audio perspective, the U5 offers above-average performance, helped along by Samsung's DNSe 3.0 sound enhancement technology. Eight audio presets are included from within the main music playback screen, including a user-defined preset that can be dialed in from the settings menu using a seven-band EQ with independent settings for bass boost and 3D.
Samsung rates the U5's battery life at an impressive 20 hours, but CNET Labs testing concluded that 15 hours is be a more reasonable expectation. Still, the battery life is about what you'll find from competitors such as the Sansa Clip or Sony B-Series, but not quite as high as the 27 hours boasted by the Philips GoGear Spark.