I highly recommend updating to 8.1. I held out for quite awhile waiting for the official update, thinking that I'd need to jump through hoops to get the developer preview...which was not the case. Enabling the developer preview is as simple as downloading the app, signing in with our Microsoft Account answering a few in-app questions. Once you install 8.1 on an 8S, it's like a new phone because you'll actually be able to install more that an handful of apps...and you no longer have to worry about your free MB of internal storage being in the single digits.
There are two very minor downsides to installing 8.1 that I've noticed... I've created a bunch of folders (using the Folder feature introduced in 8.1 Update 1) and my start screen doesn't scroll as smoothly as it used to. But this could probably be avoided by creating less or no folders. As for Whatsapp, I recently noticed that it you have "restrict background data" enabled in Datasense, it gives you a message saying you need to disable it...and you can't view your messages until you do. That's kind of annoying, but I'm not sure if that "feature" is in all versions of Whatsapp, or only the 8.1 version.
One last thing... I literally had to delete every single app, map and file from my phone storage in order to make room for Update 1. So you may have to do a hard reset at some point to clear some extra storage space for all the developer preview system updates.