Measuring Water Level in Well

Does any have any experience with the Ravensgate Model 200 or 200U. Was thinking about purchasing but have never used a sonic water level meter. Would love any input on the likes and dislikes.

Here is the link to unit
http://www.ravenscorp.com/sonic%20water%20level%20meter%20model%20200.html

I had one for about 5 years and it worked well although I didn't use it a lot. Then I quit pump work and sold it and everything else. Once in a while I'd check it's depth reading against where the wet started on the drop pipe as I pulled a pump and it was within a foot or two. I worked on submersibles mostly so I didn't get to use it through a sanitary seal but a few times.

Sounds like it worked pretty good. Thanks for the input!