A more durable, slimmer, higher-capacity iLok over its predecessor.
Definitely a sturdy little USB dongle, not going to break anytime soon due to it being made out of a single piece of aluminium. The only issue I've had is a fault on Windows' side: sometimes waking from sleep the iLok LED continuously flashes and never connects with the system again until you reboot. I believe the fix is disabling "USB selective suspend" from the Power Options plan your system is using. Haven't had an issue with it not reconnecting since.
Only good reasons to buy the iLok 3 over the iLok 2 is that you can hold 1,000 more licenses (if I'm not mistaken), its construction, the fact that it's very thin and can neatly fit alongside tightly-packed USB slots, and that in the future, some music software may require iLok 3 or better.
🎵🎵🎵 on 2018/11/24