Suggestions for textual changes:

A) 'External User Importer' screen
Change text from
Import your Principals and Groups from a CSV file. This importer will require two files, one containing your Principals and another containing their memberships (eg. "jsmith","administrators").
to
Import your users and groups from a CSV file. This importer will require two files, one containing your users and another containing their group memberships (e.g. "jsmith","administrators").*

B) 'CSV Importer' - 'Configuration' tab
Change text from
Import your Principals, Groups and their Memberships*
to
Import your users and their group memberships*

Change text from
The file containing your users information, i.e. "John","Smith","jsmith","john@atlassian.com", "password"
to
The file containing your users e.g. "John","Smith","jsmith","john@atlassian.com", "password"

Change text from
The file containing your users group memberships, i.e. "jsmith","administrators"
to
The file containing your users' group memberships, e.g. "jsmith","administrators"

C) 'CSV Importer' - 'File Mappings' tab
Change text from
Select the mappings for your Principals and their memberships
to
Select the mappings for your users and their group memberships

Change text from
Principal Mapping
to
User mappings

Change text from
Group Mapping
to
Group Mappings

D) 'CSV Importer' - 'Confirmation' tab

Maybe we should add some highlighting of some sort to differentiate this tab more from the 'Group Mappings' tab. When you click the 'Continue' button on the mappings tab, very little changes. The first time I did it, I wondered if I had actually clicked the button properly, then I saw that the tab name had changed. (e.g. different colour text, larger text, or different background colour).

Change text from
Confirm your Principal and Group CSV mappings
to
Confirm the CSV mappings for your users and groups

Change text from
Principal Mapping
to
User mappings

Change text from
Group Mapping
to
Group Mappings

D) 'CSV Importer' - 'Confirmation' tab
Change text from
Below are the results for your import.
to
Below are the results of your import.

*E) The initial Import External Users page text need to be changed to say that two files are not required, just one. ... suggestions?

*F) Change the '4. Status' tab to read '4. Results'.