I think this roaster, specifically its design focus, is not well-understood and thus some of the ratings are severely negative. After using this roaster for a year (and before using it I had used a hot air popper which burned out in 6 months) and doing some reading about others' experiences with it, I think I can offer a useful review.
Several reviewers complain about reliability and durability problems. I think these problems come from using the roaster for dark roasts requiring the roaster to operate at relatively high temperatures for relatively long periods of time. Evidently, under these conditions, the control circuitry components can exceed their heat ratings and fail. This is evidenced by at least one article on the internet which gives instructions for replacing the components once they stop functioning due to excessive heat stress. This article may be found through Google.
The more recent version of this roaster comes with two preprogrammed roasting profiles. I think that understanding the character of these two profiles is critical to appreciating and working within the limitations of the machine. The first preprogram (#1) runs relatively short and hot. It is designed for a small (75 gram or just under 3 oz.) batch of beans. I think that this program provides for the darkest roasts for which this roaster is designed. The batch size and roasting time limitations minimize the heat stress for the roaster's control circuit components.
The second preprogram (#2) provides a longer, less hot roast, suitable for batches up to perhaps 150 grams, about 5 oz. The roasting part of this program lasts 11 minutes 30 seconds. This relatively long period provides for precise control of light roasting profiles for which the roaster does very well. My own roasts, for example, of about 120 grams (4 oz. or 1/4 lb.) take from 6 to 7 minutes. I time these roasts using a kitchen timer and stop the roast when the kitchen timer rings by pushing the "cool" button on the roaster. The roasts are very uniform. I decide the specific length of roast for each bean by color and by the scent coming out of the top of the roaster. I usually stop the roast as soon as the scent no longer has any "green" bean character. Then I push the "cool" button to stop the roast. The cooling process takes 4 minutes during which the beans continue to roast somewhat before they begin actually to cool down.
Such roasts are minimal in length, providing enough roasting time to fully roast the beans and perhaps to add just one minute or so of additional roasting to provide just a bit of "roasted" flavor in addition to the complex flavor characteristic of the bean itself.
I suspect that many home roasters prefer their roasts to be darker than this roaster is designed to provide. We, as coffee consumers, have been trained by large mainstream espresso vendors to prefer dark-roasted coffee beans which are often roasted to the darkest possible brown, to an oily state, or to nearly black. In my opinion, such roasts provide more flavors that are due to the roasting process itself and are relatively independent of the character and quality of the bean involved. Certainly this is an appropriate strategy for a large commercial coffee vendor because it means that they can use all sorts of beans, in a wide range of quality, and produce a predictable product. I, like many others, find such espresso to be poor quality and unpleasant in taste. But the quality of the espresso itself is almost insignificant for commercial espresso where most of the flavors in the typical latte drinks are from other ingredients such as milk and sugar and other sweeteners and flavoring agents.
That said, there is nothing wrong with liking dark roasted espresso. It's just not the right kind of roast to expect from this roaster and to expect that the roaster will be reliable and durable. For dark espresso roasts, a much more robust, and expensive, roasting machine will be most suitable. Or an air popper which can be replaced cheaply once or twice a year.