It isn't the friendliest volume rocker I've ever had, even the Tbolt was better. I use volume control, a simple great app.

 

No problem here. I use the red case that was in all the promotional pics of the ReZound. It's just a simple snap on case but it gets the job done and looks good doing it. Picked it up from HTCPEDIA.
HTC Hard Shell Cases for HTC Rezound

 

I"ve got the Verizon gel type case and it is a pain. The volume rocker was hard to use initially now it is really almost unusable. I ended up going to the sound control (menu>settings>sound) and making all my volume settings there.

 

I use a fingernail to press up and down. Cruzerlite case with proper cutouts. The more use the better the TPC responds, a case of use it til it works. lol

 

Otterbox Defender series here and buttons work better with the case on than they do with it "nekkid".