Anybody ever use one of these? I have the need to run midi about 35 feet and want to join 3 cables with two of these. Thoughts?

I can't figure out how to post a pic but it is a Hosa GMD108

Sorry, I can't say I have any experience with those, but you might get more replies if this was posted in the Studio>Hardware forum.  

Yep they moved it to side forum purgatory

What is a MIDI splice? The standard MIDI specification allows for a cable length of 50 feet using MIDI cable. If you are using USB to connect, then it is not a MIDI signal per se, it is a USB signal carrying MIDI data and is subject to USB limitations. The USB cable length specification is 5 meters (16 ft. 5 in.). In that case you are talking about USB hubs or cable extenders. 

slart - it's not a 'MIDI splice' he used a poor choice of words to describe it - looking at the Hosa part number he provided, it's a MIDI coupler.  USB has nothing to do with what he's talking about.
 
the coupler should be fine if you are not exceeding 50' of total cable length after using the coupler(s) to connect them.  the main issue I'd warn you about would be to watch for them separating, especially if you're using these connections live.

If the case is you got 3 x 3 Mtr cable and want to reach 35 feet approx., these two coupler can be connected, also you can choose a 15 Mtr cable which will reduce the chance of getting disconnected in between.