We are solving one problem - how do we store large amounts (billions) in S3 buckets with low latency read/write access? This has been an issue since day 1 when trying to solve problems like IoT devices needing fast streaming video or high volume mobile apps pushing out realtime events across many users.
I am sure you can find other solutions but none were as simple nor solved such issues quite so well! It's not perfect yet because there will always be room for improvement however it does seem pretty good if you need lots & loads of storage space quickly available very close to your end user device (mobile phones). There are no downsides really either way apart maybe some initial setup cost which shouldnt take much time once done and definitely worth doing anyway :) Have had nothing major negative to report thus far just minor niggles here and there mostly surrounding documentation / support etc but thats expected considering this new product was built without any previous experience within Amazon ecosystem itself!