Initial connection is a bit slower than wired, maybe 20 seconds or so, but it's up and running by the time I'm moving my car.

There's very small amount of input lag for stuff like skipping songs or pause/play. I'd say that lag is almost exactly the same as when I used to only use bog-standard Bluetooth to connect to a head unit with my phone so I think that's just the downside of a wireless connection-- wired doesn't have this lag.