Bose has confirmed that currently there is no way for a user to wirelessly link a Microsoft OS desktop or laptop's spotify program to a Bose soundlink air. Only Apple products, with airplay, enable users to do this.
There is vague talk of such a link and I assume the reason why it has not occurred is because Spotify competes with services offered by Microsoft. Dont hold your breath.
I have just bought the Bose Soundlink Air and I asked before i bought it if would play Spotify. The sales person said yes and actually checked with a technican. It arrived and it set it up and it didn't work. So this morning I rang them, very polite, and they put through to a technican. And yes, it's now working and to be really honest, its brill! OK it was not that straightforward but it took 15 minutes (and I'm not a techy) and now my i-mac, both i-phones and the i-pad can connect and play Spotify so I very pleased. And the guys at Bose were excellent.