There's some very cool ideas here, I like the approach it's taking with composability, it's an interesting project. And the integration into other systems seems kind of inspired in some ways, getting a summary email or doing stuff with text messages seems gimmicky in theory but I bet it actually feels great and ends up being useful in practice. Probably a lesson there about the benefits of integrating with multiple systems/primatives that people already know how to use and build on as a way of encouraging them to be more flexible/creative.
However, and it's a big however:
Speaking as someone who once did a ton of handwritten notetaking in OneNote, and then realized that the export options at the time made it practically impossible for me to carry those notes forward as my setup evolved, and that I was about to potentially lose somewhere between 1 to 2 years of my notetaking life, the "I need to know that when I put my brain in this that I can get it back out" worry is pretty real.
It's not even just data export, OneNote had this cool thing where it would search the text of handwritten notes, which encourages you to take handwritten notes. It's great because handwritten notes feel good to write but are disorganized, so you could kind of bridge the gap. But the problem is that then even if you do get the images out, all that functionality is gone suddenly. So similarly, lets say I do use an API to back up all my notes, am I going to build extensive infrastructure around integrating with SMS and a CLI that all just gets thrown away some day?
After OneNote, it's very hard for me to consider using a notetaking app that doesn't talk about its data format/export on its homepage. Digging through the blog posts, I can see some talk about Open Source data formats, which is good, but only partially assuages my fears. But in general, /tap is immediately talking about REST APIs on its homepage, which, cool, I do think that's a cool idea. Is there actually an overlapping Venn diagram between people who are using a note system that's so comprehensive it's sending them text reminders, and people who know how to make REST requests, and people who aren't very paranoid about owning their own data?
I pay subscriptions for other people to host stuff that I don't want to dig into the technical weeds for; I pay for Wallabag hosting because I have stuff to do with my life that doesn't involve running security updates on a Wallabag server. I'm really happy to pay for services like that, especially if its in the $1-10 a month range, which /tap is. But importantly, I could self-host Wallabag if I needed to, today, without losing any functionality and without needing to rebuild any of my infrastructure that integrates with Wallabag. I could migrate my data both to the new self-hosted service or to a competing service, or I could even pay another 3rd-party to host Wallabag for me again, and point my URLs to their servers. So I don't have a bunch of hesitations in the back of my mind about giving someone money to host that kind of service because it's less of a risk to do so.
On the other hand, with /tap, with a system where I am literally putting part of my brain into the computer, I think I need stronger guarantees about how it's going to work and what will happen after it gets bought by Google.