I've been using Slideshow 2.2.7 on my front page for the last few days, and it's working great: about 15 photos cycling, in random mode, so visitors almost always have a fresh photo each time they visit.
However: the current implementation seems to choose a purely random slide to display whenever the slide timer expires. This means that photos often repeat within two or three transitions, so visitors think there are fewer unique photos than there actually are.
I'd prefer a shuffle algorithm, where a random order for the slides is chosen at the initial page load, but all slides get displayed once before any repeats show up. The order could be reshuffled each time the full set has been shown.