Our local photo club puts on monthly slide shows and it has a pretty reasonable user interface, allows integrating and timing to music, etc.

It's been around for a while but, offers a lot of flexibility in terms of output. Newer versions have improved but, I haven't felt the need to upgrade yet.

I don't much like powerpoint in this application but, it obviously works.

Choosing the right output format is important since that will drive the output resolution.