I've seen this idea submitted before, but unfortunately it's inactive. I use Spotify Premium and my car stereo allows me to like/dislike tracks, but only in Radio mode. The big reason I use Premium is because it allows me to download songs. However, unlike Google Play Music, Pandora, etc. Spotify doesn't allow me to download Radio stations for offline use. Please add the ability to download Radio stations. Thank you.
Updated on 2019-03-20
We recently changed Radio so you can now download your tracks and listen offline.
You can check out more details about this at: https://support.spotify.com/article/spotify-radio/.