Yes I'm running the latest beta. Image size for the web page I usually set at 350 or 450. source images are 1.9mb in this instance. Here's a screen shot.
Those are really small images. If the text is long (I see you are putting everything on one line) then the font needs to be small, and there is a limit to how small it is allowed to be (5 pt. minimum).
So the algorithm works like so:
(destination image width - inset%) * watermark width% = the watermark maximum width
(destination image height - inset%) * watermark height% = the watermark maximum height
Then the font starts out very large and decreases until the text fits that box, both in the width and the height, or until the font is too small to be legible.
On an 800x600 image, the watermarks are quite legible. Why 350 or 450?
-Kirk