Microemu also looks like a candidate, especially for those of us hoping to convert a midlet where no source code is available.
MicroEmu: Converting JavaME applications to the Android platform (revisited)
I've spent some time with MIDP runner and completely struck out. I've spent a little time more recently with Microemu and didn't get stuck, but just ran out of time performing a fairly complex software installation. Microemu's advantage is that it's open source, so in principle a developer would have a better chance to figure out where the target application is failing, and have some chance of modifying the emulator to meet their needs.