So I have a Motu midi XT for years. This does all that does, but is easier to set up and actually a fair bit more flexible. The software is very easy to use, and I much prefer it to Motu's unstable, inflexible oldschool editor.
I don't use the USB interface(s, as there are actually 3 USB interfaces in each U6), but they work fine and are very flexible in how data is routed to/from them.
I needed a merge box. Was contemplating another big interface, maybe something like the iConnectivity battleship... but even if you own one or more of these big interfaces, it really makes much more sense to do specific merging/splitting locally in close vicinity to the actual target machine, instead of routing midi from multiple sources all the way back to the battleship for simple merging or other processing, and then all the way back. Not good for latency, and the additional midi cables quickly add up.
So browsing the usual Midi Solutions or Kenton suspects for a cheap Merge box, I came over these. Way more flexible than the previously mentioned brands, as you can completely specify the unit to your needs. Setup changes, and now you need a split/thru box instead of merge? Just reconfigure. What I find really nice, is specialized setups like a 1 to 3 thru box, but with additional inputs with merging, so you can merge say a midi controller with an external clock or midi data, and split that to 3 unique paths/synths.
This is a great product; I got two right away, and I dont see any reason for buying something different in the future when the need for more splitting and merging arises. I found a Bitstream 3x recently on the used market; apparrently this CME is designed by the same guy. Makes total sense, as it's easily on par (or really, beyond) with the Motu XT in quality.