Wow, cool. We've got 21 Unifi AP's in various flavors running in a school environment, serving about 500-700 devices. They are very stable! The regular Unifi AP's use 24v PoE, so you either use Ubiquiti's Toughswitch to power them, the supplied injectors, or a 48v-24v dongle. I don't recommend the dongle as they overheat easily (especially if kept in a tight space), but for long cable runs, it's your only option. The injectors are good for about 50' before cable losses make the AP power cycle often.
Now, the full-on AP Pro are the way to go. We have four of them in the high density areas (Cafe, concert halls, Library) and haven't had a single issue with them. The Cafe AP Pro routinely handles 100+ clients at time, on a daily basis. What is interesting is that they will push devices up to 802.11a (iPads, iPhones, tablets) when it can, saving a good bit of spectrum. The coverage is extreme, so we run them in our fairly congested environment at medium or low power. Highly recommended.
The AP LR is the odd one, it is a standard AP (24v PoE), but doesn't get you much extra coverage. We have three of these and they tend to loaf around at medium power.
The software works very well. I have 2.4.5 running on Win7 in a VM. Guest networks block mDNS (Bonjour) so devices can't see each other. If a client needs to print, they get the coveted password to the secured SSID. Roaming works flawlessly among the AP's. The exception is the AP AC, which doesn't support fast roaming. Software beta v3 does support roaming with the AP AC, but since we only have one of those, I'm not upgrading.
Calm seas never made a skilled mariner. But, sadly I'm an A's fan.