Going to an Interview never hurts, and it is great practice with your interview skills. I got passed up a promotion at a previous job because of seniority. Which, in all honesty, it did not bother me all that much because I still got to do the back end Unix stuff of Mac OS X. However, the guy above me relied on me to get tricky stuff done. He was a cool guy though and me and him were friends, so no hard feelings about him getting the job even though I felt I was a bit more qualified. He had been there about 1.5 years longer than me. So I decided to start scouting out a new job thinking it was time to move on since no promotion was in my near future.

I had a small Linux background and this is when Apple made the first switch to Intel (about 4 to 5 years ago) and Apple started to get an increase in market share. So, soon enough I saw all sorts of Apple sys admin jobs when businesses would deploy a few macs here and a few macs there, because god forbid a Windows Sysadmin learn anything outside of Windows....I picked up on OS X rather quickly since I had a Linux background.

So, my first interview was with a very prestigious medical research firm, and they were about to roll out a bunch of Macs. The would be boss interviewed me and wanted a strong background in AD (active directory) so the Macs could play nice over LDAP. I said, OK, that is not hard for the Mac to authenticate to LDAP on an AD server. I didn't get that job but I got some skills interviewing.

In the end it was for the best. I got a new job running all the servers, managing and deploying packages, managing over 8,000 Mac clients, and so forth; and I even negotiated a higher position and higher salary than was posted for the job. All because my interview went so well and my background and credentials were sound.

So, I would say you should go to the interview regardless. Be honest and tell them you have a learning curve with AIX. Worst case scenario, you gain experience at the job interview process. That is worth it, in my humble opinion.