I've had my RNS510 for around a year now (2012 version) and its' operation seems very 'laggy' compared to the RCD510 I owned previously!
Granted, there's a fair bit more going on inside it than there was in the RCD510, but if I'm listening to the SD card for example, then I switch to radio, it can take a good 5 seconds before the sound switches over to radio. Startup also takes around 20 seconds before the buttons start responding.. if the volume key is pressed during this period, it has been known to steadily increase the volume all the way up
not nice at 7am when leaving for work!
How does everyone elses' RNS510's fare?