Good questions. Firstly though, given llamaimperative's post above, I think I should clarify that I couldn't see triple the value of Slack just by browsing the website. And while Slack has a bazillion features, I'm also well aware that most of them are so badly thought through as to be worse than useless. For instance, nobody in our company even understands what Slack's "canvas" is, or why we would use it.
So, for your questions - yeah, I definitely think a $10 starter tier would help, but I guess that would depend on what gets left out. If the story you mention in question 2 is as good as you say, I'd imagine you'd convert a lot of those users to the fuller tier anyway.
So on question 2, definitely! I could only see on the site one screenshot of the entire UI (which looks lovely btw), so it's hard for someone coming in cold to see how it behaves - I've tried out a lot of collaboration apps over the last few months and there's been more than one that looked beautiful but actually interacting with it was suboptimal to say the least. Having agreed with every word you wrote in the OP, I suspect you've paid a lot more attention to the user experience than these apps had though.
The other thing I think that's possibly missing from the website is differentiators that set it apart from Slack - the better async comms angle is up front, but as a shopper looking for a Slack replacement I want to know if this is going to solve some of my pet-peeves with Slack, like, can I actually assign tasks to other users? Does it even have the concept of tasks? Am I going to be able to hook it up to GitHub in a way that's more useful than Slack does?
There's also not much on the site about the docs / wiki / evergreen content side of things - we use Notion as well as Slack, and in all honesty we only ever signed up to Notion because Slack is like an information black hole. The idea of both of those things in a single app is appealing, especially with the backlinks feature.
Thanks to both you and llamaimperative for engaging here, would have been easy to dismiss my comment as a grumpy edge-case.
Oh, and one last thing, some of our Slack usage actually is just team members chatting as we're mostly remote - is there a space inside Campfire for more disposable type conversations?