Well, I suffer with that issue of merging contacts - name, phone, e-mail, birthday etc. info.
I backed up all my old phone contacts to Google Contacts (my old contacts were on a XLS file, so I converted it to CSV and imported it on http://mail.google.com/contacts ).
I already had a lot of Google Contacts, because of the bad default option to add everyone I sent an e-mail before...
I try to automerge contacts on Google Contacts, but it often merge wrong ones...
Merging manually on Google Contacts is so boring...
I tried some apps from Google Play to merge contacts, but they often merge wrong ones too...
Do you know a effective way to merge them automagically?