I currently switched from an iPhone back to an old Nokia, and T9 texting muscle memory came back pretty quickly.
Something I’d point out is that to change case when typing you press the
# key (on the right) not the
* key (on the left). The Mudita Pure product pics show change case on the
* key in the overview page, but on the
# in the specs page.
Not sure which is the final design, but I’d strongly suggest sticking with tradition and keeping change-case on the
# key. I suspect many potential customers will be switching from smart phones and won’t pick up on this difference until they have the phone in their hands and are met with frustration that their T9 muscle memory conflicts with the design.