Netflix is amazing for me! The HD streaming is wonderful and now that I have a second 360 I will be using it in my bedroom too!
My plan is like $16-17 a month for Unlimited streaming + 2 DVDs at a time with the Blu-Ray option. They updated Netflix a while ago to do the more active buffering changes like the Zune marketplace does. If your connection slows the video will auto adjust resolutions without pausing and then when the connection speeds up again the resolution will adjust again. Buffering on rewind/fastforward is very quick as well.