I've been testing the iPhone version of MOG, a subscription on-demand music service that I blogged about , for the last few days. While it performs adequately, I haven't seen anything that really makes it stand out from the other competitors recently, like Rhapsody, Thumbplay, and the still-in-beta Rdio.
First, the positives. Sound quality was excellent when streaming over a 3G connection and you can download any song to store in a local cache, so you can play it even when you're offline (like Rhapsody and the BlackBerry version of Thumbplay). You can choose to download songs in a high-quality (320kbps) version as well. The MOG radio feature works the same way as it does with MOG's Web-based application: it builds a playlist around your currently playing song, and a slider lets you control how much variety you want--you can play all songs from the same artist (a nice touch that free radio services like Pandora lack), or mostly songs from other artists. I was also favorably impressed with the depth of MOG's catalog, which has improved since I looked at it last year--it had selections from a local Seattle band, The Curious Mystery, that I haven't seen in too many other places, and most of the big names (with the usual exceptions like The Beatles) are present, with a full array of songs and albums.
Unfortunately, there are some problems with the playback experience. There's no scroll bar for the currently playing song, so you can't fast-forward, rewind, or move to a specific point. There's also no way to add songs to the currently playing queue--as soon as you touch the song you'd like to add, it immediately interrupts the currently playing song and skips to the song you touched. This is particularly annoying, because it does add the new song to the current playlist...at the bottom. MOG says it'll add both of these features in the next few weeks. The search function also failed with surprising frequency on single songs--it didn't find Black Sabbath's "Iron Man" or "Train Kept A-Rollin'" by the Yardbirds, even though both are in the service's library and available when you search by album or artist.
Using MOG on your iPhone will cost you $9.99 a month, which is the same as most of these other services. I still find Thumbplay to have the best user interface, and I'm intrigued by Rdio's ability to recognize all the songs in your on-device music collection and its social-networking features. But MOG looks slick and has a strong focus on sound quality, so I won't count it out.