Has anyone had to convert PatronMail or Constant Contact email addresses into Raiser's Edge? 

What do you mean by "convert"?   Do you mean import?

Did you upload Constant Contact with constituents from RE?  Did you remember to upload Bio Import ID, Address Import ID and Phone Import ID?

If not, and you simply want to create brand new records for all of these people then that should not be too difficult - it is just a new constituent import.

If not, and you have email addresses in constant contact and you want to link them to existing RE constituent records the process will not be easy.  To import a phone number to a record you need the import ID or Cons ID on the individual's record - the Import ID of the address you want to add it to and if replacing an old email address - the phone import ID of that email address.  Unless you have all of this you will either need to export it and link that export to the list from CC or manually enter the email addresses on the RE records.