Two items of note: First, FTDI released a service patch to version 1.4.0 which looks to contain many bugfixes. Second, they’ve finally gotten back to me about the specific issues I have been having trying to use the firmware in my project.
This release looks like it did fix one of the issues I had (#11), although it was only a regression from 1.2, so it wasn’t one of my original showstoppers.
FTDI also indicated that a number of the other problems are scheduled to be fixed in a 1.4.2 point release due out in mid-July. Fingers crossed.