We didn't see any credible expert reviews and user feedback is only so so 3. 9 stars based on more than 130 reviews in total split between single units and twin packs at Home Depot, and even worse scores at Amazon, though that's based on fewer than 20 reviews. Unfortunately, we didn't spot any other combination smoke and CO detectors with 10 year batteries with significant feedback and better scores. Like the First Alert SCO501CN 3ST, the Nest Protect is a combination CO detector and photoelectric smoke detector. Its feature lineup includes a night mode that prevents low battery chirps from disturbing your sleep and a humidity sensor that helps the unit tell the difference between smoke and a steamy shower. It forms a network with other Nest Protect units, and can pass information on regarding the location and nature of a detected hazard. It also can communicate with other Nest products, such as the Nest Learning Thermostat Est. $230 for example, to turn off your heating system if CO or smoke is detected. In terms of core performance, most reviewers give Nest Protect a thumbs up. It has only a photoelectric sensor, which normally will mean that it is more effective in detecting smoldering fires rather than fast burning ones and that's exactly the performance that Consumer Reports found when it tested the first generation model. However, the current, second generation Nest has a unique Split Spectrum sensor that's said to be more effective than the norm for photoelectric technology.