I can't speak to on-location digi tech work, but I also use a 2013 27" iMac with basically the same glossy screen as the TB display and I can vouch that it is beautiful to look at. Reflections aren't really an issue unless light is shining directly on your screen and if that was the case, you would have a location problem.
Matte vs. glossy is probably more of a personal preference. Glossy could have some issues with distracting reflections, but images may also feel brighter/more vibrant. I know that I can sit in front of a matte screen for 16+ hours a day without much eye fatigue, but I don't know that I could say the same about a glossy screen.