The most annoying thing that I've encountered is that sometimes the "Filling the RAM Cache" process can dribble along and take literally minutes to complete, and yet other times it will fill the cache in 10 seconds. I haven't figured out yet what triggers this. When it happens Activity monitor shows almost no disk activity and Toast is using about 20% of one CPU.
After Toast 19 finishes writing an enhanced Audio CD, it pops up with the temporary dialog box asking if you want to verify the data portion of the CD. If you just let it sit there after a few seconds it will automatically start the verification, which is fine. However, at the completion of verification the dialog box that asks if you want to mount or eject is not brought forward to be topmost on your collection of windows, even when Toast is the application with user focus. That dialog is buried behind other stuff.
I changed my preferences under Audio to make the default pause for new tracks (between tracks) be 0 seconds. This is because my source material is ripped from LPs, and already has silent periods about 4 seconds long at the end of each musical waveform. I also checked the box for "Show advanced audio mastering settings." However, when I quit Toast 19 and restart it, the gap goes back to 2 seconds and the checkbox for show advanced audio mastering settings goes back to being unchecked. What is strange is that it remembers the sound output setting, which I changed from "Default" to "Display Audio." Note that there is a misspelling on the Audio preferences page: "Prefered Language" should be "Preferred Language."
Sometimes when burning the first session (the audio track session) of an Enhanced Audio CD the status bar remains white (gives no status of how much has been completed) through all the tracks as they are being burned. When the second session (the Data session) is being written the gold status bar marches across left to right as items are burned to disk.