Spotify is a veritable dream-come-true for music lovers.

Previously available only in Europe, the music service launched Thursday in the United States to much applause. On the service’s desktop client, you’re able to listen to any of up to 15 million hosted tracks, on demand, absolutely free.

But the real gem isn’t found on the desktop app: It’s on your phone.

Spotify’s U.S. release arrives with both Android and iOS apps, which allow you to stream music wirelessly to your smartphone, via either Wi-Fi or 3G connection. You’ve also got the ability to store music files locally on your phone, so you’ll be able to listen to tracks whether you’re online or not. That’s not possible with services like Google’s Music Beta or Amazon’s Cloud Player App, which require an active internet connection in order to stream music continuously.

So what about the app itself? Here’s our lowdown on the Android version so you can see us try it before you decide to buy.

First off, there’s one caveat: You’ll have to pay ten bucks a month to upgrade to the Premium version of the service in order to use the mobile apps at all. But ten bucks a month for all-you-can-listen access to a massive music library, whether you’re at home or on the go?

Another big bonus — you don’t need to own any of the music you’re streaming to your phone in order to listen to it. Spotify has deals with the four big record labels: EMI, Universal, Sony and Warner. The tunes on your home computer get mimicked to Spotify’s servers — without having to upload them as you do with Google and Amazon’s new music services.

And it’s compatible with at least 30 Android devices, as well as iOS, Windows Mobile and even Symbian-based phones; It’s got far more reach than any platform-dedicated cloud music service.

After you’ve created a Spotify account, signing in to the mobile app takes you to a black, minimal user interface, anchored by a menu bar at the bottom of the screen. The playlists tab separates your local music — or those tracks stored on the device itself — from custom playlists you’ve created. At the top is the “edit offline playlists” button, arguably one of the app’s best features. From here, you can decide which of your tracks in your cloud library you want synced to local storage on your phone.

Why is this such a big deal? First of all, no matter where in the States you may live, there’s not always readily available Wi-Fi or cellular connectivity. Think of your underground subway commute, or maybe a weekend getaway spot in the middle of nowhere. With Spotify’s offline listening option, you’re always covered.

Second, Spotify integrates songs you’ve searched for (but haven’t previously purchased) into your cache of existing music files, treating all your tracks as part of one synchronous library. There’s no need, for instance, to switch to iTunes or your Android music player for your already purchased tracks, while jumping over to Spotify for others.

It’s meant to make Spotify your primary music playing source on both desktop and mobile devices. No Google Music Beta, no iTunes, no Amazon — no sweat.

Though you’re able to store and play music locally on your phone, you’re not realistically going to be able to store massive amounts of music on limited smartphone disk space. That means more streaming, which means you’ll have to take into consideration your phone’s data plan.

Luckily, Spotify takes this into account, letting you tweak settings to limit bandwidth usage. Choose a lower audio bit rate for streaming music, and you’ll decrease the amount of data you’re transferring (though you’ll take a hit on sound quality). And make sure you check the box to only sync your music to local storage over a Wi-Fi connection, unless you’re ready to pay some serious overage fees to your wireless carrier.

The search tab is self-explanatory. The portal allows for browsing Spotify’s massive catalog by track, artist or album title, and we’ve found it damn comprehensive.

Although to be sure, there are some glaring omissions: Songs from bands who are notorious for tightly guarding their catalogue rights — The Beatles, Led Zeppelin, Metallica — are nowhere to be found, with only tracks from god-awful cover bands to fill their stead. That may be a dealbreaker for you, but really, how many times do you need to listen to Abbey Road?

The ‘what’s new’ tab adds a social element to the app, split into three further category tabs at the top of the screen. The ‘what’s new’ and ‘top tracks’ categories are fairly straightforward, as they’re basically lists of recent additions to Spotify’s catalog and the most popular songs at the moment, respectively.

Let Spotify connect to your Facebook account, and the third ‘feed’ tab is a bit more fun. It’s literally a newsfeed of the music your friends are sharing on Facebook. Right now my feed is sparse, as I’ve only a handful of European Facebook friends using the service, and even fewer U.S.-based Spotify pals. If it takes off, however, I’ll soon know which friends of mine I’d go to shows with, and which ones have musical tastes that mean I’ll never look at them the same again.

Afraid your friends will peep your expansive collection and see something you’d rather them not? Don’t worry, Spotify included a way to share only the playlists you want to make public, so your Bieber-fever can forever remain a well-kept secret.

It’s worth noting that competing service Rdio has most everything Spotify offers, not to mention Rdio has been available in the states for almost a full year. But with a music catalog that beats Rdio by more than 40 percent, Spotify’s lofty aspirations are promising.

Of course, we can only wait and see what sort of traction the service makes in the States. If the Android app is any indicator, we can see Spotify living up to the hype.