Are there any drawbacks to using this service?

This service should not be used if you store restricted data.

Rules and profiles in the shared firewall are not customizable.

The only services on the protected side of the firewall that can be accessed from the unprotected side are printing and remote desktop services. These services can only be accessed from non-Calvisitor campus addresses.

Campus vulnerability scanners are allowed and there will be no firewall exceptions for devices that have issues with scanning

Since systems using the shared firewall service are not isolated from each other,  malicious insiders may still be able to access the systems on the protected side of the firewall.

This service can only accommodate entire subnets. If you only want a subset of your systems to use it,  those systems must be put on a new network.