Comma-separated files are good if you guarantee that the data field contents won't itself contain commas. Otherwise, tab-separated would be the way to go.

Comma separated:

repout.writeline(objgroup.cn & "," & objmember.displayname & "," & objmember.samaccountname & "," & objmember.physicalDeliveryOfficeName & "," & objmember.title & "," & objmember.department & "," & objmember.mail)

Tab separated:

repout.writeline(objgroup.cn & Chr$(9) & objmember.displayname & Chr$(9) & objmember.samaccountname & Chr$(9) & objmember.physicalDeliveryOfficeName & Chr$(9) & objmember.title & Chr$(9) & objmember.department & Chr$(9) & objmember.mail)

ETA: You may have to drop the $ signs, depending on the VBA version (i.e. Chr(9)).