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I have been reading with interest the sonar usage (right sensor, etc.) because I had already purchased the previously recommended sensor (EZ0) but had yet to add it to my quad. After reading the posts by Maxbotix and others, I went ahead and took the plunge. I added a 100uF capacitor directly to the board (photo above) as recommended and put a 100ohm resistor on the +5V line.

I created a cable and hand-braided it in an attempt to eliminate as much noise as possible.  I know Maxbotix recommends a shielded cable but I didn't have any.  The cable is also a little too long.  I also temporarily mounted it to a paint stir and put it on the opposite side of the air-frame from the receiver.  But as you can see from this photo, it is darn close to one of the prop tips too.  But enough of that - how did it perform?

Here is the result of a test flight in pretty high wind.

The red is the sonar height, the green is the barometer height.  At no time did the actual height get above 10m during my test.

First, I am continually surprised at how accurate the barometric height is.  Second, the sonar trace has some decent readings for much of the flight, but sometimes is has crazy readings.  I can't tell exactly what is going on here yet, but I'm going to track it down.  I know the sonar I have is ultimately too sensitive and is probably picking up things like the mailbox (which was certainly nearby).  Additionally, I wonder how likely it is to be hindered by heavy winds?

I'm going to do some more testing soon.  I want to shorten the boom to get it further from the prop.  If anybody has any testing methods they think are good for sonar units, please let me know.