You don’t need to be a mechanical engineer to know that is contraption is going to feel very uncomfortable to hold.

There are actually a bunch of other negatives that the cofounder did not mention. You will also lose the ability to quickly type emojis(might actually be a good thing). No more autocorrect/prediction and the keyboard is missing some common symbols such as angle brackets.

Another likely problem with this keyboard is that the keys are too small because they are round. Square keys were the common choice for most cellphone keyboards for this reason.