I've been testing jsr with some packages. The experience was good in general but I would like to drop here my impressions, I hope you find them useful.
I used to avoid unnecessary typing in my TS code but seems that the new TypeScript checking for JSR (called FastCheck) is much more strict than the Deno default configuration (which was also quite strict). This made me think about one of the main flaws of Deno (in my opinion): The segmentation of the developer experience.
I had the same feeling before when Deno Deploy was released. Everybody assumed that you could deploy your Deno code until we realized that Deno Deploy is not the same as Deno CLI and doesn't support the same features. This difference between both runtimes has a reason (and it's understandable), but it breaks the expectation and introduces friction in the Deno ecosystem UX.