On its own iLuv's new Rainbow8 does what a HomeKit bulb needs to, and should satisfy most people. A poor app and a lack of IFTTT or Alexa integration, however, may mean there are better choices.
Arguably, easy setup is the main reason to get the bulb. Because it uses Wi-Fi instead of Bluetooth, and there's no extra hub to connect to your router, setup is ridiculously fast and simple. Once it's screwed in and turned on, all you have to do is load up the Rainbow iPhone app, tap the "+" button to add an accessory, and scan your HomeKit code -- voila, you're connected. Like any HomeKit gear, you will need an iPad or Apple TV to serve as a hub if you want control outside of the house.
The Rainbow8 supports 16 million colors and is rated at about 800 lumens, roughly equivalent to a 60-watt incandescent bulb. You may need 2 to 4 to adequately light anything but a small room, in other words. It's brighter than some LED options, but not as powerful as what you can get from companies like LIFX.
In testing we also found that veering away from white could sometimes significantly diminish brightness. That's actually a common problem with color-changing smartbulbs, but something to consider if you plan to bathe a room in a particular shade.
Full brightness in white, red, and light blue tints.
A little more troubling is that the color wheel in the Rainbow app doesn't always correspond well with real-world output. We sometimes had to fudge our color selection to get what we were expecting, which is ultimately just an inconvenience yet still disappointing.
The app as a whole is arguably the weakest part of the product. It's serviceable, but sometimes counterintuitive. To control a single bulb for instance, you can tap on its icon once to turn it on or off, but have to tap and hold to see color and brightness settings. All three of those options should be accessible from the homescreen. We did at least appreciate the ability to save five favorite colors through a bulb's settings, not to mention options to quickly rename a light or assign it to a different room.
There are other awkward design issues. Despite HomeKit integration, the only scenes that show up on the homescreen are ones you've created with the app -- you have to hit the "Rooms" tab to see everything. Some parts of the app have badly-written English, and if you want to reset a Rainbow8, you'll have to delete its entry and flick a power switch on and off four times.
It's best to control the accessory using Siri or iOS 10's Home app/Control Center extension when you can. All of Apple's standard options apply -- you can tell your iPhone to "set the Tall Lamp to pink," for instance, or use 3D Touch in Home to quickly access brightness and color settings. The bulb integrates seamlessly with scenes, and of course supports standard automation options like timers and geofences.
What it doesn't support though is Amazon's Alexa assistant, or IFTTT (If This Then That). You may not care about Alexa if you have an Apple Watch or an iPhone with you at all times, but IFTTT hooks into so many other hardware and software platforms that support may be a legitimate reason to go with other smartbulbs.
Conclusions
It seems to us that the Rainbow8 is best suited to people who don't have heavy HomeKit demands -- say, someone living in an apartment who just wants to set the mood for a movie, or have a few lights turn on and off when they come and go.
Beyond that though, it's better to invest in lights with a complete ecosystem. The Philips Hue platform may have its critics, but it integrates with Alexa, IFTTT, and HomeKit, and has a range of bulb types and switches, not to mention a better app. LIFX doesn't support HomeKit yet, but it should soon and it already works with Alexa, IFTTT, and some specific accessories like the Nest Thermostat.
Score: 3.5 out of 5
Where to buy
The Rainbow8 costs $49.99 from iLuv or third-party vendors like Amazon.