Both Nokia and Microsoft were once titans in the smartphone world, but the pair have struggled to find favor with consumers, carriers and developers in the iPhone-Android era. Now, the two companies, which have become close partners, hope they've finally found the formula for success. The product on which their hopes rest is Nokia's new flagship smartphone, the Lumia 920, running Microsoft's revamped operating system, Windows Phone 8.

I've been testing the Lumia 920 and consider it a handsome, high-quality phone with attractive features that worked well for me. Not only that, but it costs half of what most other top-of-the-line smartphones set you back, and yet gives you twice the typical memory. It is greatly improved from the first flagship Lumia, last spring's Lumia 900.

While this isn't a review of the new Windows Phone 8 software, I can say that it also has improved in the past year. Its underlyingarchitecture has been rebuilt, it is faster and more reliable, it now has smaller icons so you needn't scroll as much to find what you want, and it still offers a fresh, engaging interface that sets it apart.

But the Lumia 920 has two big drawbacks: It is heavy and thick and, like all Windows Phones, it has a much smaller app selection than the iPhone or Android phones.

This new Lumia, which costs $100 with a two-year contract from AT&T, has a sharp, vibrant 4.5-inch screen, a very good 8.7-megapixel rear camera, and is fast and fluid. It supports LTE, the most consistentlyspeedy U.S. cellular-data technology, and has 32 gigabytes of memory for storage. It is made of plastic, but it is a solid-feeling plastic in bright colors -- including red, yellow and blue -- that are injected into the material.

The phone also has some unusual features. Its screen responds to fingernails and even fingers clad in regular thin gloves (though winter-weight gloves didn't work for me). And it can be charged without plugging in a cable, by merely placing it on a charging plate that plugs into the wall. (The charging plate, normally a $49 option, is being included with the phone for an unspecified period.)

While I didn't do a formalbattery test, this Nokia lasted me through a day of mixed use. Voice calls were reliable and clear, and the phone's speakers sounded great. Photos and videos looked very good.

In my tests, the LTE speeds were very good, averaging 17 megabits per second downstream. But AT&T's LTE network is only in about 100 cities.

However, the Lumia 920 has a few characteristics that may turn off potential buyers. The biggest downside is its sheer size. This may be the heaviest modern smartphone I've tested, and it's one of the thickest.

To give you an idea, it's 65% heavier than Apple's iPhone 5, and 40% thicker. We're in an era of smartphones with larger and larger screens, but most phone makers take care to keep these bigger-screen phones relatively light and thin, something Nokia didn't do here. For instance, compared with the latest high-end Android phone, Google's Nexus 4, which has an even larger 4.7-inch screen, the Lumia 920 is 33% heavier and 17% thicker.

The second major downside is app selection on the Windows Phone platform. The number, quality and variety of apps has improved considerably in the past year. But developers still either ignore Windows Phone or write for the platform well after they've launched on Android or Apple's iOS mobile operating system. The Lumia 920 has about 120,000 apps, versus some 700,000 for the iPhone and the latest Android phones.

Sheer numbers of apps may seem irrelevant after a certain point. In fact, important apps like Facebook, Twitter, Netflix, Kindle, Yelp, the New York Times, and Words With Friends are available on the Lumia 920 and worked in my tests. Plus, only Windows Phones have smartphone versions of Microsoft Office programs.

But my searches of the app store on the new Lumia failed to turn up plenty of popular apps available on the Apple and Google platforms, such as Instagram, Dropbox, Google Drive, YouTube, HBO GO, Spotify, Pandora radio, MLB, Scrabble and Starbucks.

Some other annoyances turned up in my tests. An update to one of the built-in settings features has remained stuck in the app store for days (Nokia can't explain why). The camera, which claims superior image stability and low-light performance, generally did very well for me. But it sometimes had a tendency to take over-bright shots. For instance, an orange wine label came out as yellow.

Voice recognition is a weak point on the Lumia 920. Its ability to answer spoken questions and commands lagged far behind Apple's and Google's in my tests. And its dictation capability for things like email and texts was atrocious, never coming close to accurate.

The wireless charging plate worked every time for me. But it has a gigantic wall adapter and takes about an hour longer to charge the phone fully than the included standard charger cable.

All in all, though, the Nokia Lumia 920 is worth considering, if you can live with a heavy device -- especially given its combination of low price and strong features.