Spotify hasn't even been available in the U.S. for an entire year. Still, its growth has been phenomenal, and it appears to be continuing unabated, thanks in part to its deep integration with Facebook. The product's other big initiative of the last several months has been its third-party app marketplace, which extends Spotify's desktop functionality by leaps and bounds.

When the service finally did launch in the U.S. last July, I tried it for 48 hours, then swiftly dumped both Rdio and the iPod app on my iPhone. After all, Spotify combined the giant streamable cloud library of services like MOG and Rdio with the ability to sync local MP3s to your device, just as you've always been able to do via iTunes. Each month when my checking account is debited $9.99, it's primarily that mobile listening experience that I'm paying for (along with the absence of advertising). For the most part, it's worth it.

Having used the service on my phone everyday for the last eight months, I've developed a list of things I wish it did better. None of these things is enough to cause me to think twice about my subscription, but when a mobile app is weaved this thoroughly into your day-to-day life, you tend to grow a little picky and particular about how it should work.

1. Improved Social Features

When it comes to social media integration, Spotify's mobile app scrapes by on pretty much the bare minimum. You can share songs via Twitter and Facebook, and under the "Friends" tab, you can view playlists from your Facebook connections. That list includes everybody you know on Facebook who has signed up for Spotify, even if they aren't active. As a result, I've got a lot of people in my "Friends" list with absolutely no music saved. This isn't at all useful to me. Those people could be easily filtered out.

The potential here is practically limitless. Spotify's Facebook integration presumably gives it access to data about which songs are shared most widely. Tapping into Twitter's API could allow them to build a list of songs that are currently trending on Twitter, as well.

Spotify already has a list of your social connections, but they could be baked into the mobile experience a little more seamlessly. Music-sharing could be expanded beyond the usual players, as well. Social integration into music services isn't necessarily a nut anybody has cracked yet (just ask Apple), but if anybody is well-positioned to do it, Spotify is.

2. Spotify Needs an iPad App

The iPhone app for Spotify works perfectly fine on the iPad, and doesn't even look that bad when blown up to double its original size. But in this day and age, the tablet form factor calls for an application that takes true advantage of the screen real estate and user-interface possibilities.

MOG and Rdio, Spotify's two chief competitors, both have iPad-specific apps and they both make effective use of the bigger screen. Rdio launched theirs a few weeks after Spotify launched in the U.S., and MOG just released an iPad app a few days ago.

Granted, streaming music is probably more suited to the smartphone experience, but at this point, enough people are using their iPads as a sort of impromptu radio at home to justify making the experience as enjoyable and tablet-appropriate as possible.

3. Make it Easier to Browse by Album

One thing that's always bugged me slightly about Spotify is its user interface is not very album-centric. New releases and search results are easily browsed by album cover, but one's own collection is basically a gigantic list of songs. In fact, the library itself is just a series of playlists, which includes starred tracks, your inbox and local MP3s, as well as any other custom playlists you've created.

By comparison, when you're browsing your music in Rdio's mobile app, it feels a lot like the iTunes UI, in the sense that content is arranged by album. It's a natural and intuitive way for music to be organized. As a result of the way Spotify is designed, I find myself using shuffle and playlists a lot more, rather than listening to albums from beginning to end.

4. Subway (or Airplane)-Friendly App Launching

This one might seem a little nit-picky, but the last time I was in New York, I rode the subway from Queens to Manhattan to attend a conference and made the mistake of not launching Spotify before the train went underground. What I didn't realize was that the app needed to re-authenticate my log-in info before the service would work. Thus, I couldn't listen to any music during my subway ride, since the app needed an Internet connection to hit Spotify's servers and log me in, even if all of my music was cached locally.

Apparently, Spotify needs to log you in every time you launch the app. I'm sure there are legitimate technical and security-related purposes for this, but it's inconvenient when you're not able to get online, and all you want to do is access your local MP3s and cached songs.

The easy way around this would have been to launch the app before losing connectivity, but you'd think that an app designed to work offline wouldn't have this weird little limitation.

5. When Will Those Third-Party Apps be Ready For Mobile?

One of the most exciting things about Spotify's desktop client is the third-party app platform it launched in December. By mashing together Spotify's API with other services, the platform opens up enormous new possibilities for the service.

Early partners include Pitchfork and Rolling Stone for audio-augmented album reviews, Last.fm for music recommendations, Soundrop for group listening and MoodAgent for tonal analysis and song-matching based on the mood of a given track. And this is only the beginning. There are a number of other apps on the platform, presumably with more to come.

Naturally, Spotify can't fit every third-party app into the limited real estate of its mobile applications. There are design, technical and, in some cases, legal issues to consider for each one. Presumably, the best of these apps will find their way to mobile platforms as quickly as is feasible.

6. Personalized Recommendations, Please

Another thing that Spotify does reasonably well in a desktop environment is offer personalized recommendations to music fans. Their Last.fm integration does a great job of this, and other Echo Nest-powered features such as Spotify Radio could pose a legitimate challenge to services like Pandora.

The ability to stream songs based on an individual song or artist, as Pandora has done for years, could be a huge bonus for mobile users. Incorporating MoodAgent's emotional analysis could play a key role here as well. Whether a user wants to discover new music based on their existing tastes or just isn't entirely sure what they want to listen to at a given moment, a more serendipitous listening experience would be a worthwhile feature to have in a mobile context.

Personalized recommendations are relatively new to the Spotify desktop client, so we're not surprised that it's not available for mobile users yet. Like the third-party apps, it's something that is presumably on its way.