Yes, I too have one of these cards, left over from many years ago.
I did buy a GM car (a 2000 Pontiac Firebird) at the end of 1999. My spending on the card helped me save nearly $2000. And I'm still driving the Firebird.
I don't use the GM card anymore, though. I haven't gotten around to canceling it - there's no annual fee, so there has been no rush to cancel.
When I talk with my wife about it, she says that she now absolutely refuses to consider buying a "government car." So it doesn't look like we'll be purchasing a new GM vehicle anytime soon. So the GM card just stays in the drawer while I carry other cards in my wallet.
I also receive those "top off" offers every now and again.