Edit: I also use Google Maps while talking, or check for movie times while someone is on the phone.
I too don't put much value on the simultaneous voice/data feature, but then again I have 2 phones, so I usually multitask by using two devices. Even without that though, I've never really felt a huge demand for the voice+data thing.
// edit: for whoever downvoted me: The more steps it takes to reproduce an issue, the less likely someone is to complete all the steps and run into it. The OP listed three steps, that will only happen under rare circumstances (people don't normally go to concerts every day).
I'll tell you what has come up for me, though- the Pre's UI for multi-tasking is way better than that found under iOS. There are a lot of things I dislike about the Pre, but the WebOS UI is not one of them. If only I could merge the hardware and app selection of the iPhone with the UI of the Pre... well, a guy can dream.
Here are cases I've used:
1) Take a call while tethered (I think USians on AT&T underestimate this use case)
2) Send an email while on a call a discuss to discuss attachements. (PDF, image mockups, etc)
3) Send an iCal event and juggle schedules to meet
4) Take a call while running with RunKeeper in the background
5) Refer to Twitter DMs while on a call
6) Sync DropBox/iDisk while on a call to talk about documents
7) Look up directions on Google Maps for the caller
8) Look up movies on Flixster and decide which movie to go to.
9) Play games while on holdAlso, the limitation only applies to cellular data; anywhere a Verizon customer has wifi they can use both.