As someone who entered the professional rat-race after completing my undergrad degree, I can tell you with certainty that TAing does give you invaluable experience that you can use to your advantage when applying for and starting a professional career. There are so many skills that you use regularly as a TA - you are expected to mentor other students, present in front of large audiences, synthesize and summarize accuratelky, and it indicates an ability to work under another person in a non-research capacity.
I was an undergraduate TA, and I was able to use that experience to get my first job after completing university. While many academics may look at their experience in university as only preparing them for academic work, the most successful of us are those who can see the skills we gain in university as TRANSFERABLE, and can market them as such.
I think TA experience would be even more important for a professional program, since your end-goal is likely to work in the private sector. Any experience you may have working in your chosen field will benefit you when you graduate. TAing definitely qualifies as work experience. One of my TA positions was for a qualitative research methods class, and when I was looking for work in the public opinion research industry (which is what I currently do), I was able to demonstrate that I had a thorough understanding of the methods employed by people in my chosen industry because I had taught them to other people.