I'm in love with the Spotify service and love it very much and has been subscribed since the early beginning in 2009. However, trying to minimize the offence, I must say that when I tried Rdio, I feel how 'outdated' I feel Spotify is in it's design. Rdio has virtually everything Spotify has, plus a bunch of features Spotify refused to provide to their users for some ugly reaseons - playlist text, publishing collaborative playlists, a web based client (that enables users on lockdown areas to enjoy the service), an well developed API that is available for all platform - including streaming by common protocols.
While I don't want to swear in the church as this does not mean that I not longer like Spotify, I still love it because it is in Sweden (Maybe I can work here sometimes in the futrue), Daniel Ek is a pioneer and the name is genious. But Rdio has been able to take the steps further that the spotify community has suggested through the years without any answer.
With a technical knowledge I may believe the lack of development in those areas that Rdio has a more well-developed aspect, I bet it's by the core design of Spotify. Spotify has from it's core to front-end at most been a closed, lockdown propierty protocol from it's back end to all clients. This was in the beginning mandatory to get the labels on the road, but for now, it seems like the P2P transfers and the refusal to go beyond their own protcol and make use of standard technologies (except for the in-closed applications) may be the death setence for the service in the future.
But as you have done amazing thing for us I don't stop believe in you. I think you are working on a HTML5 online client (you aren't fooling) and you are soon releazing very amazing things that will impress the whole community within a few months this year (My astral belief and feelings says you have something amazing to show by the end of the year). But currently I feel that Rdio has a more modern aspect of their development of their service, for example the collaborative playlists, where they actually could be published without any problems.
Throughout the latest years, I've experience somewhat spiritual trips to the Spotify office during my REM sleep and got insights that I probably can't share with you to not risk reveal any business secrets as it might be remote viewings.