IF you’re wondering WHERE in the world your newly validated card is, the card doesn’t show up on every Twitter client. Here’s my experience so far as of 2012-03-14:
On Twitter’s website?
Yes. That’s the only place I see the card. There is a delay as @froginthevalley points out (thanks!). Here’s mine in the live: https://twitter.com/ctessmer/status/444633964825694208
On Official Mac Twitter client 3.0.1?
Not a trace.
On iPhone iO7.1 Twitter client 6.2.1?
Yes. But they’re hidden in people’s timeline. A teeny, tiny, minuscule, little (get the point?) icon appears next to your tweet in users’ timelines. (Well, mine anyway). (Maybe it’s expanded in other people’s?)
When click on the tweet, it expands. Then it looks REALLY nice.
This causes me, however, to rethink my “marketing strategy” with cards and tweets. For me, I rather include a picture the normal way, so twitter can display it loud and proud in users timelines. So maybe for twitter, instead of having ONE image, I’ll have two. One for the card (as it’s generated on my blog) and another to manually attach an image. Not sure if or how that will work. But. Gonna give it a whirl perhaps after I get some sleep.
Hope this helps some human out there.