Same. I switched to spotify (and spotify radio, which is free) a while ago. But I still scrobble everything and it's cool to look back! Not to mention you can do a lot with the data.
I do the same. You can fill in your last.fm username in Spotify. Spotify also has an last.fm app. The music you listen to scrobbles to facebook as well as last.fm.
Edit: Oh I think he meant, scrobble in the sense of keeping track of what you listen to. You don't have to keep using the last.fm desktop client.
Unclear what you mean. They both scrobble, do you aggregate them together someplace?