It's been burning fine at 24/96 for me. At least according to the DVD player. And it's taking up most of the DVD, so it's got to be a larger file than a 16/44.
Gaps, I've had no issues, but others in the past have said they did. As mentioned in an earlier post it was suggested that you have to burn the image to your HD first, than use a seperate program to burn to DVD.
Don't know about cue and txt files, haven't tried.