When performing an import to overwrite existing contact records you currently have to match duplicates using up to 3 fields.
While that may be OK in some instances it doesn't function very well for those users who have duplicate records.
I have quite a few customers who purposely have duplicate records because they use ACT! in innovative ways. Because ACT! is limited in certain areas ie: Performing more complex calculations in fields or just replacing parts on a field value rather than the whole field, they have to export data to Excel to perform the calculation and then re-import it back into ACT!. That is when the problem arises namely that the data mixes up which record it belongs to when it imports.
A simple solution to this would be the ability to export the database Contact ID and then use it to match dupes on re-import.