I'm a Spotify dev. What sort of data would you find most useful to have extracted from iTunes?

The reason we don't do the smart playlists is that we just take a snapshot (the lists aren't kept in sync) and the very nature of smart playlists is that they are dynamic.

Even a snapshot of smart and dumb playlists would be better than nothing. The use case is, users who want to migrate to Spotify from whatever they've been using for years, intend to copy over their playlists to Spotify, and permanently switch to Spotify as their main playlist organizer/generator. But having to recreate all their playlists by hand in Spotify is enough to stymie even the most enthusiastic US/NA Spotify fan.

Same problem on the Android app I just discovered yesterday, all my local playlists are made with a third party app called Playlist Builder, and both PowerAMP and Google Music can use them, but apparently not Spotify. I only have Premium, but it seems Premium is intended to enable local music and playlists just not sharing and streaming...

You can drag a playlist from iTunes and drop it on the "New Playlist" button in the left sidebar in Spotify. I don't know if it works with Genius lists, but it works with "Recently Played" and other dynamic lists.

What format is Playlist Builder using, m3u perhaps?

.m3u8, all stored in what appears to be /Playlists, though my phone isn't rooted so I'm not sure if that's the highest level of the directory structure.

Well, I find rating songs very important to my own music discovery. I have around 6500 songs in my collection, about half of it rated, and all of it meticulously genred. Making playlists and picking something to listen to is really easy, as is downloading something new and incorporating it into my playlists.

Find a new reggae artist, rate his songs, and boom, next time I'm listening to good reggae, his songs pop up (but just the good ones).

Spotify makes all of my ratings and all my playlists useless. And it is therefore not very useful to me :/

I see how rating helps with making playlists from your own library of already rated tracks, but could you explain how it helps with discovery of new artists?