I used to use one to control a 4 manual Allen in the choir loft from a 4 manual midi console downstairs. It was a long distance - maybe 150 feet.
For the most part, it worked quite well, but there were occasional glitches that caused notes to hang. MidiWorks said it could be cell phone interference, humidity, any number of things. We never did solve the issue.
I finally went back to the midi extender from Artisan that works over cat-5 - worked flawlessly for years.
The MidiJet was around $500 - the Artisan $65. But you have to have cat-5, which we did.
Hope this helps.
Steve