I don't see why people make a big deal out of this. How often do you really need to talk AND use data at the same time? I've never, ever, ever, ever, ever had to or even had the inclination that I wished I could. I think it's one of those features that sounds cool, but in reality no one really uses.
I use it all the time. I'll often be on the phone (using a headset) and pull up information online, or send out an e-mail to someone on the con-call, or pull up a new document in DropBox, or.....
Add in using it a Wifi hotspot, and getting your VPN connection/download/SSH session/whatever interrupted every time your phone rings would be REALLY annoying.
I've often gone through the steps of saying "hold on" while on a call and launching Safari, Mail or some other app to check something that was being discussed (e.g. "Did you get my email?" "Not yet, I'll check now").
It'd be worse if you're using it as a hotspot and you're sharing the hotspot with other people.
Actually it's one limitation about CDMA that I hate. I would love to use one of the reverse lookup apps to get details about unknown callers but I can't because the operation of receiving the call means it can't simultaneously do the lookup.
I also hate having some sync operation get stopped because I get a call.
It's more annoying than you think but not a total deal breaker.
I work out of coffeeshops occasionally and use my Nexus One as a wifi hotspot to avoid unencrypted public networks (which is free for me on T-Mobile by the way). Its awfully nice to be able to take a phone call and hold on to the data connection so that I can continue working while on the call if need be.
I needed it recently--I was driving around downtown LA while talking to a friend and trying to use Google Maps (he was trying to guide me somewhere and I was having trouble finding it). In that case I happened to have spotty coverage and my phone switched to edge and so I couldn't do it and that was adding to my frustration.
Also talking on the phone and needing to look up a reference happens surprisingly often. It's really nice to have data available while talking.
For myself quite often. My boss calls me and lets me know that 'x' server is having 'y' issue. I'm on my phone's wifi hotspot so I'll log into the server and answer questions while we talk over what is going on.
I don't see why people make a big deal out of this. How often do you really need to talk AND use data at the same time? I've never, ever, ever, ever, ever had to or even had the inclination that I wished I could. I think it's one of those features that sounds cool, but in reality no one really uses.