Many Insteon devices are currently supported, including the powerlinc modem, switchlinc, lamplinc, and keypadlinc. I do know of at least one user who cannot get the Insteon PLM to work with LinuxMCE, for unknown reasons to me.
Just last month I updated the Insteon PLM drivers to include support for Insteon Motion Sensors. Because of that, I have a good understanding of ddamron's drivers, and I might be able to help you if there is a feature that is not included.
I have also been working on a way to create Insteon groups from the LinuxMCE side of things. Currently, Linuxmce handles Insteon devices within lighting scenarios by sending an ON command to each device separately, so if a room has five lights each one will turn on sequentially about one second apart. The proper way to handle this would be to add those devices to an Insteon group and then send a broadcast command. Also, because the drivers are written in Ruby instead of C++, multithreaded ON commands are also not possible unless someone were to rewrite the drivers in C++. I think there is a version of the driver in C++, but I'm not familiar with that.