Any help, pointers or suggestions are much appreciated!
Hi Jeff,
Apple has already announced they will reinstate "autocomplete text in cells" so providing feedback on it probably isn't necessary. Until Apple reintroduces it sometime within the next six months (and even after it is brought back) you should consider formatting the cells in the column as Pop-Up Menu if you frequently enter repeating values in a column and don't want to type the same text over and over again.
In many situations, particularly if you are worried about typos, Pop-Up Menu has clear advantages over "autocomplete" anyway. It is much enhanced over what it was in Numbers 2.3, and is very easy to set up:

Select the whole column before formatting as Pop-Up Menu and your existing values in that column will pre-populate a menu automatically:

Then you can remove the values you don't want in the list, such as the column header (and possibly some previous spelling errors too!):

And after this easy one-time setup all you have to do thereafter is to choose from the pop-up list when you add rows:

See this post for more details on how this handy feature has been enhanced in Numbers 3.0.
In Numbers 3.0 there is no keyboard shortcut to activate the menu such as hitting the spacebar in the old Numbers (hope they'll add one in upcoming versions) but the Pop-Up Menu approach has some advantages over autocompletion: no spelling errors or lack of capitalization when there should be capitalization, etc.
And should you ever want to take your Numbers with you, in a touch interface pop-ups are much more efficient than typing the first few letters of items. You can scroll with ease through a list of dozens of items to make a pick.
See this thread for this and other workarounds for Numbers 3.0.
SG