ALL REVIEWS

Let me first say, I'm a huge fan of the Nintex products, especially Workflow. The product in general helps me deliver huge value to my clients. I also should say I love trying new things and then telling other people about them. So, when I found out the Nintex Platform Preview was available, I jumped on it. 
Within 5 mins of having an Office 365 SharePoint 2013 online instance up, I had already added the Workflow Platform Preview and was designing my first workflow. Sure, it didn't do much (wrote something to the history list) but the fact that it was all so easy was fantastic. I've not yet had the chance to use lots of the actions but I also love the fact you can see the Nintex guys making changes to the available actions. It will be great to see the updates they make over time. 
Get this free app, give it a go, you'll be mightly impressed at the simplicty and power.

I've used Nintex Workflow with SharePoint 2007 and 2010 - and it's the best way to get workflows for documents, lists and forms - much easier than SharePoint Designer or Visual Studio - and I was pretty excited to see that you can now do the same with Office 365+SharePoint 2013.
Many of the same activities are still available for 'online' - and there's also the 'LIVE' bits, for posting to Yammer, FaceBook, etc - or currency conversion, language.
The new HTML5+jQuery designer looks very slick too - and installing it is simply a one-click 'Add An App'.  
If you haven't used workflow before, Nintex is a great way to get started with it - give it a try - you'll soon wonder how you lived without it !