After a couple of days of working with it, I'm starting to get used to it. I kind of wish entering notes was easier -- I keep getting confused between what the left-click button does and what the right-click button does.
Try "Rex Mundi" input mode (you can set this in File>Preferences). Then you just mouse over where you want to place a note and then press the 1, 2, 3, 4, 5 or 6 number key to add a note to that lane (lane 1 is the bottom-most string). Right click will bring up a context menu, but the edit pro guitar note function is a couple levels deep into that.
And I kept wishing the right-click button would call up the Fret number/Finger number dialogue -- partly because I'm mostly working with the mouse, so having to go to the keyboard all the time is difficult. And THAT's partly because I had a guitar in my lap the whole while so I could verify the notes I was tabbing in, so my fretting hand was usually holding the guitar.
I'll see if I can make middle click (ie. clicking down on the scroll wheel) can bring up the edit pro guitar note dialog for selected or moused over notes. But that will only work if your mouse has a scroll wheel and Allegro can reliably detect it.
I would like to put measure+beat+tone (first one can be just base tone name) to some text file and it would be processed when RS XML is exported. It can be in song.ini for all I care, but timing by measure+beat would be as convenient as it gets.
I probably won't add support for an external text file just for this, but I may reconsider beat text, but it would have to be formatted pretty specifically (ie. "tone:[tone name here]").