[officialtony]

I have never used the Tack-It.
I have used the Velcro strips. They work great when you are wearing the patch you need. The problem is when you have no patch on the shirt, the Velcro looks like crap. If there is no patch attached to the velcro, it picks up lint, etc. If you can come up with something to put over the velcro when you are not required to wear a patch ( like a US flag ), the velcro may work. I have even tried to put just a blue patch over the Velcro ( or whatever color matches the shirt you are wearing ), but it is still clearly visible.
Unfotunately, I have found no effective way of swapping patches.