I'm chuffed (as the Brits say) that SoundSlides is now available in Beta with the option to produce the audio slideshow so that it's iPad compatible. In fact, version 1.9.4 has a couple of options related to the iPad. The first option is to have the slideshow only readable on iPads, whilst another is an iPad-auto-detect.
I've tried the auto detect option on three audio-slideshows, and they worked pretty well. However, I haven't been able to remove the Captions and Credits buttons (which I don't want) from showing up on the iPad, and I understand that this will be fixed in a future version.
The other issue which I don't think is fixable relates to transitions. The transitions look somehwhat choppy on the iPad...presumably due to its processor and browser. One of my audio slideshows makes use of the "flip-book" technique which relies on a large number of stills with very short time intervals to give the appearance of motion, and this feature doesn't show well on the iPad at all. It just shows the first and last frame.