The HTC Radar 4G ($99.99) is the first smartphone in the U.S. to ship with Windows Phone 7.5 'Mango'. Mango is a smooth, compelling update that can win you over if you're tired of your older iPhone or Android handset. Thanks to Microsoft's tight restrictions on design, all Windows Phone devices work more or less the same; the trick is finding one that appeals to you from a visual and tactile standpoint. To that end, the Radar 4G is better than most.

Design and Call Quality
The Radar 4G measures 4.7 by 2.4 by 0.4 inches (HWD) and weighs 4.8 ounces. It feels classy, thanks to its svelte design and mostly aluminum back panel. The white and silver color scheme looks distinctive, although some may find the combination off-putting—especially around the back, where the white plastic wraps around to a significant extent. The 3.8-inch, 480-by-800-pixel display is suitably bright and colorful. It's also just large enough for comfortable on-screen typing in portrait as well as landscape mode.

The Radar 4G is a quad-band EDGE (850/900/1800/1900 MHz) and tri-band HSPA+ 14.4 device with 802.11b/g/n Wi-Fi. Compared to the blazing HSPA+ 42 on the Samsung Galaxy S II ($229.99, 4.5 stars), that isn't real 4G. Voice quality is just OK; callers had no trouble understanding me, but the earpiece has a tinny quality to it that isn't particularly pleasant. There's no Wi-Fi calling, either; normally that's not an issue, but T-Mobile's coverage is weak in my part of Massachusetts; without it, I couldn't complete some test calls, while others dropped the moment I stepped back inside the house.

Calls sounded clear through a Jawbone Era Bluetooth headset ($129, 4 stars). Voice dialing worked fine over Bluetooth. The speakerphone sounds poor, though, with a tinny tone and not enough volume to use in a remotely noisy environment. Unfortunately, I couldn't get a reliable battery result, thanks to the choppy reception.

User Interface, Apps, and Multimedia
Touch response was stellar, and scrolling was every bit as smooth as it is on an iPhone; Microsoft has done plenty of work to nail the UI experience, and it shows with Mango. The sliding panels and tiles that update in real time make this handset distinctive, and just as enticing as an iPhone or Android device. The 1GHz Qualcomm Snapdragon MSM8255 processor isn't dual-core; credit Microsoft's stringent spec for the OS. It's sufficient, but it does position this (and all) Windows Phone devices as decidedly midrange.

Otherwise, it's standard fare for a Windows Phone device: You get comprehensive Microsoft Exchange and Outlook sync, a Microsoft Office-compatible document editor, and a solid WebKit browser. TeleNav GPS Navigator is also on board for voice-enabled, turn-by-turn directions. Windows Phone 7 smoothly integrates your Facebook contacts with the built-in address book, as well as around the rest of the OS, which is something the iPhone could learn from. That said, if you love apps, you should go with Android or iOS; there are much less third-party apps available in Windows Phone 7 Marketplace than there are in the Android Market or Apple's App Store, a situation that will likely continue for some time.

You get 6.08GB of free internal storage, but as is typical with Windows Phone devices, there's no memory card slot. To sync music, videos, and photos, you can use either Zune software for a PC, or Windows Phone 7 Connector for a Mac. I chose the latter for this review, and had no problems syncing with both iPhoto and iTunes. A standard-size 3.5mm headphone jack sits on the top edge of the phone. Music tracks also sounded clear through Samsung Modus HM6450 Bluetooth headphones ($99, 4 stars) and the built-in music player is fun to use. Standalone video files played smoothly in full screen mode and looked vibrant, and 1080p files transcoded on the fly.

Camera and Conclusions
The 5-megapixel auto-focus camera comes with an F2.2 lens and LED flash. Test photos were about average, with good light balance and color accuracy both indoors and outside, but not as much detail as I expected given this level of sensor. Recorded 640-by-480-pixel (standard VGA) videos are reasonably smooth at 22 frames per second, but could have been a bit sharper and more vibrant. There's also a 1-megapixel front-facing camera for video chats. 

Windows Phone 7.5 has an uphill battle, but it's not because of the quality of the OS. If anything, it's a real contender next to Android and iOS, especially in the midrange of the market. It just needs more higher-end devices and apps to level out the playing field. If you're game for something different, Mango is worth a look, and the HTC Radar 4G is one of the most economical devices with which to experience it.

Otherwise, while T-Mobile is the only one of the four major carriers without the iPhone, it does have plenty of stellar Android devices. The HTC Wildfire S ($79.99, 3.5 stars) is probably the closest approximation to the Radar, with its slick HTC Sense UI and Android 2.3 (Gingerbread) OS, but it's screen is smaller. The Samsung Exhibit 4G ($49.99, 3.5 stars) isn't as attractive and has a more basic Android build (which can be a good thing), but it offers HSPA+ 21 data speeds and a faster 1GHz processor. The Samsung Galaxy S II is our current Editors' Choice for T-Mobile touch screen smartphones, with its brilliant 4.5-inch Super AMOLED Plus screen, dual-core processor, and ultra-fast HSPA+ 42 data speeds.

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