I just received my temporary certificate and when I called the airman registry to ask how long it would be before I received my permanent copy, they basically told me it was going to take awhile. So my question is, what can I do with the temporary? Are commercial jobs allowed? Can I apply at private companies to fly for them?
A temporary certificate is valid for everything that a permanent one is valid for; it's just, well, temporary.
No person may serve as a required pilot flight crewmember of a civil aircraft of the United States, unless that person:
(1) Has in the person's physical possession or readily accessible in the aircraft when exercising the privileges of that pilot certificate or authorization—
(iii) A temporary certificate issued under §61.17;
A temporary pilot, flight instructor, or ground instructor certificate or rating is issued for up to 120 days, at which time a permanent certificate will be issued to a person whom the Administrator finds qualified under this part.
(See this question for what happens when the 120 days are up.)
As far as the FAA is concerned, your temporary certificate is no different from a permanent one. I suppose it's possible that an employer might decline to hire you until you get a permanent certificate but I think that's highly unlikely within the US (employers abroad might be a different story). I've seen people pass a CFI checkride and start instructing within a few days, for example.
A temporary certificate has the same privileges as the permanent certificate. A temporary certificate expires after 120 days.
If you temporary certificate is about to expire, you can have a new one issued on the spot at an FAA FSDO, with an appointment. If the FSDO is not convenient, there is a way to request an extension online.
Temporary certificates are commonplace, as any pilot adding a rating will receive a temporary certificate.
Most permanent certificates have no expiration date, but common exceptions are CFI and Remote Pilot certificates.