Pros and cons below.... but look; Powerpoint, as a program, is an embarrassment; It's overly complicated yet incredibly underpowered for its complexity, and I dislike using it every single time I have to.
Dectopus, on the other hand, is FUN to use, INSPIRED me to improve on some aspects of my most recent presentation, and delivered a FAR SUPERIOR presentation in a FRACTION OF THE TIME it would have taken with Powerpoint.
If you truly use the ever expanding 1001 features lurking behind Microsoft's myriad ribbons, then Dectopus might not cut it for you (although conversion to PPT is remarkably easy).
If time is money for you, and you need to make great looking presentations, quickly and efficiently, that are 100% portable, the Dectopus is a NO-BRAINER.
THE PROS:
Great UI
Lovely designs.
Some good font pairings (Some not so good, too, but style is subjective and most are spot on).
The style swap is fun, and the vast majority of styles are really well considered.
Rehearsal mode looks interesting.
Video slides are easy.
Presentation creation is quick.
Presentations can be viewed from anywhere with a browser.
GIF search is FANTASTIC. This is a very cool feature that livened up my last rush presentation really nicely.

THE CONS:
Personal taste issue; but I find only about half the palettes appealing. Some look great, some look less than great.
Font pairings are very limited (although mostly really nice).
Export is currently only in PDF. (This can VERY easily be converted to PPT online, and is apparently being considered for Dectopus)
The image size slider/controls are tiiiiiny, and don't seem to allow 100% zoom out.
Fullscreen mode can be glitchy, especially when using video. I briefly lost my Next/Previous buttons when using a video and got stuck.

What I would like to see:
CNAME
PPT export
Increase the number of font pairings available (Although allowing from other template packs would probably be enough)
Allow me to use font pairings from different templates.
Allow me to make my own colour pallets.
Allow me to convert one slide layout into another. For example; if I have a text only layout slider, and would like to add an image, or icons, I have to start again.
Allow me to control the caption size on image slides.
It took a while to figure out slides had to be dragged to the 'New slide' button to rearrange them. Please consider a larger target area (full vertical between slides?)

I have recently only had time to write reviews for deals I find VERY promising.
The team at Dectopus seem to be answering questions and reviews very well/quickly/thoughtfully, and are apparently ready to step up and deliver on some exciting sounding improvements.
The software itself already saved my backside, allowing me to create a presentation in less than a third of the time it would have taken using Powerpoint. Not only that, but the presentation was far superior. I received lots of praise afterward, and the entire group were smiling.
Definitely a good deal.