Slingmedia just released their new version of Slingplayer Mobile. Version 1.6 is now available for download in the US and UK.
The new version is available for Windows Mobile Smartphone and Windows Mobile Professional devices (both 5.0 and 6). If you are already licensed then it's a free upgrade. If not they do have a 30 day trial too!
They also released an updated S60 client too.