Great letter. I have sent similar emails to MBTA here in the Boston area and gotten a relatively positive response- or at least a "we'll look into and inform the driver".

To balance the scales a bit. I have also written letters praising those drivers that give me or other cyclists proper space and respect.

Positive reinforcement can have at least a noticeable effect as criticism at times. I also have written to the agency which oversees maintenance of the bike path and given lots of positive reinforcement every time they plow the bike path in a timely and effective manner. That way when my emails of "disappointment" come they seem to take them seriously. I have noticed some improvement to the plowing but, of course, that could be coincidental.