I do like it at least once a week.
I do this thing where I put on a stream and have no idea what songs/bands are going to be played, so I use it as an exercise to see how quickly I can figure the song out and how close I can come to matching the general tone and phrasing by the end of the tune. It's especially helpful when there are a lot of songs I have never heard before, so I do this a lot with current Alt and Indie rock (still has to be guitar music after all). I do find that it keeps me sharp and gets me out of my head a bit as I don't have time to thing about what key things are in or where they are going, just gotta naturally get there quick without thinking, and I really like to try to anticipate where they will go with the bridge once I get the basic sequences down. If there is a solo in the song I will often improvise one, which is another nice exercise in itself.
I don't play along with music that I know unless it just happens to come up in the stream, and even then I will usually skip a song I know.