I am a radiologist and I have previously tried wireless headsets, desktop mics and other handheld mikes. I now have 2 speechmike IIs and use 2 at work. I find the speechmikes the best that I have come across. I have no experience with the series III speechmikes.
Speechmike functions and buttons are completely configurable. This needs to be done properly with your speech recognition software. I use Dragon Medical. I would recommend going for the speechmike version with buttons as opposed to the slideswitch, (which I found difficult to configure). Also the version with 4 extra buttons which also are fully configurable is more useful. The device produces key press combination shortcuts which are matched with dragon functions.
The device works quickly you will not have a pause providing you have the speech software running already) you get a visual recording red light on rec. I use a single button push to turn rec on and then off- not holding a button. The trigger on the underside does not get accidently pressed. I find the quality good and I have no failures in 3 years.