It's worth noting that newer Ubiquity APs no longer support Zero Handoff. Part of the problem was that all the APs needed to be on the same channel, which cause

It's worth noting that newer Ubiquity APs no longer support Zero Handoff. Part of the problem was that all the APs needed to be on the same channel, which caused co-channel interference under heavy usage; there was a significant performance impact. (Also, I believe that chipset in the newer Unifi models just don't support it.) Without it, clients can still roam between APs, but you'll notice ~1 second of packet drops each time your client roams to a new AP. It won't drop a VoIP call, but you'll notice a moment of silence when it happens. The future is 802.11r/k/v, which will allow clients to roam themselves quickly between participating BSSIDs without needing to renegotiate the connection each time (as opposed to relying on pure AP-based hacks).