I would prefer the option of choosing checklist or checkbox as the list style. In the meantime I came up with another workaround. When making my list I choose bullet list for the style. Then I select the items I want checkboxed and add checkboxes using the option under +. New entries need checkbox added but at least adding items won’t convert previous items on your list.
There is a 50% discount currently for first year of Premium. The upgrade link popped up on my desktop version of Evernote last night. I had been considering Plus since i have more than 2 devices in use. Normally I would not even consider Premium because I can't justify adding $70 to my budget at this time. With the discount came to same as one year of Plus. I expect I will downgrade after the year is up unless some decent discounts become available to entice me to stay with Premium.