I've been very discreet about mine. I haven't even told my mother. Only two people have ever commented on my Invisalign. One of my outspoken colleagues noticed right away and said "Oh, so you got braces?!?!?" And after five minutes of speaking to my sister in law who hadn't seen me in months, she blurted "oh so you got Invisalign!!! How do you like it?!?"
Both of these people are very familiar with Invisalign because they have had close friends/family members who wore Invisalign. So I think people may notice it more if they've seen it before.
Invisalign:
23/31 U (2/3 done!)
6/6 L refinements; Completed 15/15 L
Metal braces 10 years ago