Not a whole lot to say about this, other than what was said in a tweet from @Spotify:
A couple of interesting things to note, however. First off, we think that this is the first third-party app that we’ve seen with Voice Actions. Can you think of anything else? Second, you’ll need to be running Android 2.2 in order for the update to work, as Voice Actions are a FroYo-only feature.
Oh, and there’s also the issue of one of the voice commands not working. A European friend of mine keeps trying “open service in the US” and nothing ever happens…
For those of you who live in areas that can get Spotify, you should find the update available in the Android Market.