I see my indicated signal strength fluctuates as well. However, I've never dropped a call yet, the other person's voice always sounds better than it ever did on my Moto Droid and Droid Bionic (same calling areas) and the person that I call the most (namely, my wife, who has been historically very persnickety about how I bad I sound on a cell phone call to the point that she'd rather hang up as soon as possible because she get so frustrated by not being able to understand what I am saying very well) has said that my voice is as clear as can be.
So, yes. I realize that others have had call dropping issues, but what was the control in that study? Side by side or memory? I don't doubt that in some areas the effect of poor signal is real. However, in the relatively boonies, where I live, I LOVE, LOVE, LOVE, the clarity of my voice calls. I think I'll just keep ignoring the dBm meter and bar count on the phone and move on.
Edit: I just left a voicemail on my office phone with zero bars indicated when I dialed and -120 dBm signal strength in the phone status area. I could hear my greeting loud and clear and when I listened to my voicemail from the landline - it sounded clear, one small bobble in one word, and waaaaayyyy better than the similar tests that I had performed with my Droid. Take it FWIW, YMMV, etc, etc, etc.
Edit2: screen shot of a Speedtest with zero bars 3G is now attached. I'm not disappointed at all. I suspect real world problems with signal are less than being reported, but just how it is the signal is displayed... Again, YMMV.