I am also disappointed that there will be no irclone
support. I have recently purchased the URC-200
and hoped that irclone coming which would have
been a bonus. Although I have not used an MX-500/600,
the coding in irclone should not be too different
for the URC. I suppose 3 versions would be required,
i.e. URC-100/200/300 which complicates the situation.

The alternative to irclone is a less elegant solution
and involves using an OFA or RS to “learn” those
special or discrete codes not found on the original
equipments’ remote control. A more involved process
involves use of JP1.

Here is an example of where it would help me.
I have a Sony TV and Receiver and a remote controls
for both. The TV remote control has a single on/off
button, no discrete. The Receiver remote control
knows the discrete code off code for the TV, and
uses it as part of an internal macro to turn everything
off. The sequence is long and cannot be learned
by the URC-200. I need to program this code into
a remote and then learn it to my URC-200. This
is going to get worse when I get my Denon 2805
and Samsung HLP.