Spotify launching in the US at 8AM tomorrow, open to all pre-registered users

We can hardly believe it ourselves, but we just spoke to someone from Spotify with a totally American accent and confirmed that the unlimited music service is indeed launching tomorrow at 8AM ET. While the service will be in a limited “beta” rollout initially, we were told that everybody who has already requested an invite should hopefully get in on wave one -- though there weren’t any promises, so if you haven’t pre-registered, we recommend doing that right now and putting on your lucky beta-testing socks tomorrow. Once you get in you’ll have access to a library of 15 million songs, which you can enjoy for free with ads, $5 a month with no ads, or $10 a month to include your mobile and higher bit rates in the mix -- right in line with services like Rdio and Mog, except for that sweet, sweet ad-supported option. Oh, and let’s not forget Spotify’s real killer feature: a truly great native application for Mac and Windows. We suppose we’ll find out tomorrow if the middle of 2011 qualifies as “fashionably late” in our already-crowded subscription music scene, or if Rdio, Mog, Rhapsody, and Zune can hold onto our fickle mainstream hearts.