Visitor ID has been used for over 2 years now, with no issues or complaints from our end users (our clients). It works as expected 99%+ times without issue which makes it easy to get things done when we need them! Nothing so far really though - there are some minor quirks here & then but they can be worked around fairly easily if you know what your doing! We use this primarily at work where people come into office buildings all day long using their own devices etc., usually not connected via VPN / Wifi networks either :-D.