We recently had our electrical panel replaced/upgraded and I noticed that our GFCI breaker was replaced with an Arc Fault breaker. Is that safe? Are GFCI breakers obsolete now?
GFCI are still needed because ACFI do not provide the same level of ground-fault protection as GFCI. In the United States, the GFCI is triggered at 4-6 mA of current-imbalance. The trip-limit for AFCI devices is a current-imbalance of 30-50 mA. So AFCI devices do not provide the same level of ground-fault protection as GFCI devices. You may want to use both an AFCI and a GFCI on your circuit.
In addition to ground faults, AFCI devices do also detect arcs. GFCI and AFCI are designed to detect different faults from eachother.
GFCIs are still needed near sources of water (like the kitchen and bathroom), in unfinished basements, and outdoors (among other locations) (and even if the circuit uses an AFCI breaker).
Arc-fault circuit interruption (AFCI) devices typically offer ground-fault protection of equipment (30 mA and higher), but not ground-fault protection of personnel (4 - 6 mA). If ground-fault protection of personnel is required by code (damp, wet, etc. locations), you'll have to install a GFCI device along with the AFCI device.
Check the devices that were installed, and insure that they provide the proper level of protection.