I'm finding the iphone queue to be frustrating and inadequate. First of all you can't see it. Second, it's impossible to clear it. If i queue up 10 songs for a workout but finish before the end of the queue, then try to play an album by clicking that album's first song, spotify will play only the song i've selected, finish the queue, then play the rest of the album. You cannot even skip forward through songs you've queued when you come back to spotify after exiting. I don't know if you can skip through queued stuff during the session you queued them. Rdio has made their queue available on all devices and has even synced it. Why does spotify even have a queue on the iphone if it's going to work in this unintuitive, and lacking fashion.
While we're on the topic, rdio seems to keep improving it's design and feature set while spotify's interface is mostly static (and ugly), or getting useless new features like follow (ping for spotify). If you're going to copy something it seems like you wouldn't copy a failure. If it weren't for local music integration missing from rdio, I'd have gone over long ago. I'm very curious how improvements to spotify get prioritized.
I wish that spotify would open up a rich api so developers could build music applications for people who are interested in having a rich music listening interface.
Finally, rdio actually gives you the ability to reach out directly to them. I feel like that is very telling with regard to the way the two products are shaping up. On the one hand spotify has chosen to only have this forum which I assume they peruse, but definitely don't respond to 100% of. On the other hand Rdio lets you email them directly and a human responds, fairly quickly I might add.