I just got off the phone with the Sling PR folks and have confirmed the current version of SlingPlayer Mobile for Smartphones is not compatible with the T-Mobile Dash (likely my next phone, despite the lack of EVDO). Sling is aware of issue and already has a beta build in testing for release in the “near future.” Once distributed, the updated software will also have improved support for all Windows Mobile devices.
And yes, a publicly available version of the Mac SlingPlayer is still slated for release this month!