With regarding to PDF annotation, I wonder if Mantano could have some difficulties implementing a better interface due to its use of Adobe's Reader Mobile...? Cause Adobe Desktop Editions also has no PDF annotation support whatsoever.
Would be nice if a Mantano staff can drop by and explain a little bit.
FWIW, ezPDF seems to be using xPDF (
http://www.glyphandcog.com/Xpdf.html). Not sure what RepliGo uses.