Are there tax benefits for employers to hire military vets and/or their spouses? What other advantages might there be?

A quick search provides many results. This one is a good quick-summary:

http://www.businessweek.com/news/2011-11-30/obama-signs-law-granting-tax-credits-for-hiring-jobless-vets.html

As former military, I can tell you that relative to the age of the person you are hiring (compared to college graduate) you will be benefiting from someone who takes their job very seriously, demonstrates maturity and responsibility. If targeting experienced veteran, you will be getting someone who has managed millions of dollars in assets, trained and evaluated dozens of young men and women, and can ease into a role of leadership very naturally.

Don't be thrown off by the misconception of ex-military as robots or non-free thinkers. Couldn't be further from the truth. Also, you have literally hundreds of job-skills to choose from in terms of training. There are aviation engineers, military police, safety inspectors, adminstrative gurus, translators. Not everyone was trained just to point and shoot.

Also, if culture is important to you, each branch of service varies in terms of "relax fit" vs. "hard charging". Air Force, Navy, Army, Marine Corp. all very different and you can find individuals who would not put off your employees by being dictatorial.

Good luck if you decide to hire veterans. I did not mention this, but there is also the sense of giving back to those who serve when you implement a conscious hiring plan including Vets.

I believe the only benefits, other than the quality, is a public relations benefit:
-11.08.2012 - "G.I. Jobs and U.S. Veterans Magazine on Thursday recognized the ongoing commitment of U.S. Bank in employing veterans."
-02.13.2012 - "G.E. to Hire 5,000 Vets, Expand Aviation Operations."