Take a look at Allanah's Resource Page

Good things

• Drag and drop image
• One click to improve readablility
• Would be nice and simple for kids to add stuff from their drive
• The site shows up as part of Google Drive for editing- like a slide set might
• Site navigation top right- doesn't seem to be able to love it or do anything interesting with it.

Still drives me crazy.......

• Can't centre Google Slide Set
• Can't embed html
• No gadget insert
• Two kinds of font to choose from and that's it
• Can't find a way put text over image title or edit anything other tan cropping an image
• Things very linear in nature- can't put stuff where you want them to go.

Verdict

• Don't feel you're not missing out on anything by not having it yet.
• From the look of it you have to publish in similar way to old fashioned SAVE (PUBLISH) if you want changes to stick.