Mapping works fine for me, but when a contact's (address) details are changed it doesn't always update the geocode lookups.
Currently (1.9) this doesn't happen - verified on demo.civicrm.org as well as our live install. Tested on 2.0 sandbox where it seems to happen occasionally.
1. Update a contact's address details, so that a latitude and longitude are set for the address.
2. Change the contact's address details to a different address.
3. Verify that "Map this address" still directs the user to a map of the old address.
On 1.9, clearing the stored lat/long values before saving doesn't appear to help - it doesn't trigger a new lookup, but it does remove the "Map this address" link (of course).
On 2.0 (sandbox), editing an existing contact in the system (Test Test in sandbox) didn't update the geocode results. Creating a new contact, mapping them, then changing address and mapping them again (Nijo Lakaaakra in sandbox) worked as expected.