I love my Manta and definitely wish I bought an e-ink note taking device sooner. After researching the competition, I decided on the Supernote Manta due to its size and the company's prioritization of the customer. Modular design, DIY sections, and the lack of a subscription fee were critical factors.
Using the Manta has been awesome. It truly feels like writing on good paper and its layer functionality is a game changer. Want to make a list of key tasks and then add some superficial information you'll need for some of the key tasks, you can either: A) add new pages or B) add a new layer. I find myself loving the ability to add a layer because now a single page can get me through complicated tasks without needing to scroll. While it will take some trial and error to learn the best directory/note structure for your use case, the overall feel is quite intuitive.
My one complaint is the lack of device encryption/"secure operating system". I would love to be approved to use my Manta for work items, but the outdated android base system and lack of device encryption are complete blockers. Even with that limitation, I still use it for non-internal work documentation. Think of reference guides or public requirements documents. It's far easier to digest these documents on my Manta, then use my own notes/digests as a reference guide to craft internal documents/solutions that align and cite industry standards and expectations.