I got it about the same time the US embassy stopped giving residency affidavits. I used the yellow book to purchase a motorbike.
I use the pink ID as my ID often instead of my passport. I have a Thai driver's license but I usually show them the pink ID.
I opened a bank account recently using my passport, yellow book, and pink ID. As an American I was expecting resistance but they were actually very welcoming and it took less than an hour to set up the new account. I can only speculate that having all three ID's helped smooth the way.
I was recently inquiring about getting a tax ID but, as someone else mentioned, my tax ID is my pink ID. I saved some money and effort not getting a tax ID.
Slightly off topic - I needed to get a login to my US Social Security account. There was an identification process and the pink ID turned out to be the only photo ID with my current address.