Hi David,
Even after "auto-complete" is brought back you might want to 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 want to avoid typos or capitalization inconsistencies creeping in and messing up your data, Pop-Up Menu is better than "auto-complete." It is much enhanced over what it was in Numbers 2.3, and is easy to set up:

Select the whole column or range before formatting as Pop-Up Menu and your existing values in that column or range 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).
And should you ever want to take your Numbers with you and do data entry on an iPad or iPhone, 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. Anybody using Numbers cross-platform should favor Pop-Up so they can use their documents efficiently for data input on the go, which can be a productivity booster.
Also, auto-complete is not as good a choice as Pop-Up Menu even for keyboard-intensive work on the Mac if you've got numerous hard-to-spell values, particularly if some are capitalized and some not, where the capitalization can be significant. The Pop-Up Menu approach, unlike auto-complete, eliminates spelling inconsistencies or lack of capitalization when there should be capitalization, etc.
See this thread for this and other workarounds for Numbers 3.0.
SG