I've been using his product religiously since they've been available. Unfortunately that's the crux of his products: they're often not available. Ubiquiti does a fantastic job of engineering and marketing (online), however when a new product hits their page - it's often months upon months before distributors get product. That being said - it's some of the best wireless gear for the money. Their new 1Gb+ (AirFiber) link hardware is pretty awesome, and in general I won't buy consumer grade wireless junk (i.e. Linksys, D-Link, etc) anymore since I can outfit clients or family with hardware like UniFi very cost effectively.
xxiao - not sure of what you mean by "mesh" but AirOS (and pre-AirOS) has supported WDS for quite some time.
AirOS and everybody else has WDS these days, Mesh is different that uses AD-HOC mode(check meraki.com, google olsr, 802.11s etc).
Routerboard is actually also great hardware vendor, and cheap too. However it's not in US, and it sells licenses with its software with a premium, which is not attractive to customers, esp those in other developing countries. UBNT wins the battle easily with great hardware, and most importantly, free software going with it.
xxiao - not sure of what you mean by "mesh" but AirOS (and pre-AirOS) has supported WDS for quite some time.