first of all, thanks for the magnificent piece of software
second, sorry for digging this thread up, but i'm facing the same problems (SL vs DL speeds)
replying to your problem, i ask you if this can work out:
somewhere in a menu, you put a checkbox 'remember media type (or code) burn speed'
if this option is enabled, imgburn would start with that value pre-selected, but users would be able to chenge it afterwards, just like the current version
or:
you colud also add a dialog box (just like the benq advanced options or booksetting) in which the user selects the maximum desired burning speed for -r/+r/-rw/+rw/ and cd.
when you press burn, if this option if set, the program would use the user inputed values, if not, it uses the normal speed drop-down box selection.
i'd say the second option is more reliable and easy to implement. as far as i can see, there's no incompatibilities of any kind, as the users only activate this option if they want.
if you want to discuss possibilities for this feature with me, please feel free to contact me or reply to this post.
thank in advance