Windows Mobile is graced with Spotify right now & will also be present with WP7
Handset owners can simply download the app by pointing their web browser to m.spotify.com and manually select their specific version. However, it's worth noting that the best Spotifiy experience can be found on devices like HTC HD2, HTC Touch Pro2, Samsung Omnia 2, and Sony Ericsson Xperia X1 & X2. From the looks of it all, it doesn't seem to pose any issues for any high-end Windows Mobile handsets, but it may not provide the same resounding experience on older sets.
Regardless, it's here and available for the taking which will provide some entertainment on the go. Additionally, Spotify will be there from the onset with Windows Phone 7 and will make its presence known primarily in the European market.