Recs.
Updated
SpecsUpdate
Pros
Pro Desktop and Web versions
You can use it on any internet enabled device. It also has both Mac and Windows applications.
Pro Works with Pocket service
Pocket is a popular service included with the Firefox browser and Premium e-readers such as the Aura Kobo One. Pocket allows users to save articles to read later or archive them for saving. Asides from the convenience of saving articles for future use it also formats the text and images beautifully. Stubborn advertisements typically get left behind as well. Having easy access to narrated Pocket articles is a convenience auditorily and visually.
Pro Limited free account available
For feature differences and limitations of the free version visit captivoice.com
Pro Semi-desktop and web app versions make it pretty much cross-platform
You can use it on any internet-enabled device. The desktop macOS and Windows versions uses your default browser and Java to drive a web app. On Linux you'll have to use the website or run a virtual machine. On macOS and Windows, the "desktop app" is more than just a shortcut to the website - everything required to run the app is stored locally and persists after deleting browser cookies & offline data.
Cons
Con Subscription service to get extra features
In order to get some extra features, you have to pay for the subscription service which is $1.99/month or 9.99/6 months.
Recommendations
Comments
Out of Date Pros + Cons
Con User must host files
Capti Narrator does not host your files, a user must use a service like Dropbox or similar for documents ebooks etc to be available cross-platform. Seems strange since Capti Narrator processes the files, someone would think that the content would be on their servers. They should offer to host the files for a more robust syncing experience.
Con No desktop version for the mac
Only available as full native apps for iOS and Windows, otherwise it's desktop browser and bookmarklets.