Yes, long tap (or tap-n-hold) will snap a picture. It spot-focuses then snaps. Sure beats the jitter that comes with pressing the trackball. I wondered why that was the direction on-screen, seems HTC would program it to tell you the long-tap trick.
I also noticed that with 1.5 you can flip the trackball a time or two and the zoom comes up. With 2.1 you get a little +/- button and when you press it you can swipe-n-zoom===much handier!