I Love my Linn streamer. When I was considering its purchase I wasn't sure exactly why I needed it as my computer is on most of the time I'm home anyway.
But having lived with it for over a year now I couldn't imagine life with-out it.
I will say however that it is not quite a plug n play device, it has required some technical upkeep & experimentation. Which for me is an added bonus, but won't suit all potential users.
Not to mention the hours that I've spent ripping CDs & tidying up meta tagging. Don't think that you're going to plug you old itunes library in & everything will be in the right place. This may not bother some, but for a neat freak like me it needed to be fixed. Now that I'm almost finished, starting to reap the rewards however, an immaculate library is a thing of joy.
Apparently Linn are about to release a new UPNP set-up called Kazoo which will work in tandem with their Songbox server software. In the final stages of development, dues some time in the next few months I think. This will replace Kinsky which is not loved by all.
I regularly use Spotify via air-tunes with no issues. The Songcast app is functional, but often feels like a tacked on second thought. Not sure if it's becase I'm a Mac user or some network issue, but I find that it's sound quality is not as good as the DS & it seems to break after every firmware update.
This is a thread on the Linn development forum which talks about Spotify integration, with a few interesting comments by a Linn staffer as to why they have chosen not to go in this direction:
http://forums.linn.co.uk/bb/showthread.php?tid=25723
I have also found this article to be helpful is grasping the building blocks of a DLNA based network system:
http://www.computeraudiophile.com/content/524-complete-guide-hifi-upnp-dlna-network-audio/