The cloud-based aspect of the Google apps remain the #1 feature, and the ability to access my docs from anywhere (regardless if I'm on my computer or a public computer) is stellar. Google Slides provides a superior experience when collaboration with others is essential, natively tracking changes (like who edits what) and allows viewers to comment without making changes.
Much like with Google Docs, there just aren't enough slick and beautiful features to make an impressive presentation. Google Slides is a good place to start gathering ideas for what an eventual PowerPoint or Keynote presentation might look like. If you really want to see this in action, create a presentation in PowerPoint, upload it to Slides and see what happens. At least half of the formatting is missing in Google Slides.
I'm not sure I can recommend Google Slides to anyone who is serious about making a nice presentation. It's great for sketching up ideas, but it's the right tool for a real professional presentation. If that's what you're after, you should avoid Google Slides and go for something like Microsoft PowerPoint.
Google Slides doesn't have the same benefits as its other apps (Docs and Sheets), but it remains a good option for when a group needs to collaborate on the structure of a presentation.