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You should go to admin -> field management and review the mapping of you key fields. If you have performed the recommended operations before Jan 31st, you fields should be mapped with SFDC fields that are prefixed with "mkto71" and not "mkto2".
If this is the case and you fields seem to not sync anyway, then it can be related to the Marketo user accessing the fields in SFDC.
Now, with regards to the person object, it makes NO difference at all. Marketo Lead used to map with lead and contacts in SFDC. The Marketo lead has simply be renamed as Person, but the mapping is unchanged.
We created and mapped to mkto71 and everything looked right for the switch over on the 31st.
All of the mkto71 fields in SFDC have for for some reason overwritten as mkto2.
Any further ideas?