Kevin Thacker released a new work in progress version of his Amstrad CPC emulator called Arnold. For this release he did a huge amount of testing, especially for the FDC routines, and wrote a lot of tests to ensure that the emulator behaves just like the real machine.
You can get a precompiled version here: http://www.cpctech.org.uk/setup.zip
And for the Linux and Mac users (and Windows users :-)) – you can get the source code here: http://www.cpctech.org.uk/arnoldsrc.zip
Here is the changelog for this version (be prepared… it is huuuuuuge):