Well looky here! Evidently Microsoft has introduced some new plans for the Zune Pass. Whereas before it was just a monthly pass for $14.95 and included 10 song purchases, you can now do 3-month ($44.97) and more importantly, annually for $149.90.
The annual plan is the sweet one as $149.90 works out to $12.50 a month, which is a nice savings (basically get "2 months free").
You can sign up or upgrade now and may be something worth considering when you get your Windows Phone 7 device. As for myself...already went annual, not even a question.