In my experience, yes they are quite reliable.  If you just started testing this and immediately found it is not working, I think it is more likely that there is a logic error in your workflow design than a lack of reliability in the Nintex architecture.  Its hard to know what you might be forgetting without having more details on your configuration.

We use them in approval workflows and have not ran into any issues.

I have them setup with a 10 day escalation, which in turn cancels the requests and then notifies the user to resubmit if it is still needed.

I am planning on adding reminders for the approval task so we can reduce the number of auto-cancelled requests, just have not implemented it yet.

As an alternative, you could always setup a site workflow that queries your desired list and based on some logic (if [today] = [Created] + [escalataionTime] for example), and handle the notifications that way. A little more effort required especially when the action can handle it for you.

Hope this helps!

My logic is very simple. I create a new item and start a workflow with a single Flexi Task. Due date is set on the initiation form which makes the task due now.

On the reminders tab I set the number to 2 reminders every 15 min.

On the Escalation tab I set it to 1 hour.

30 minutes after the workflow started still no reminders... I assume that with the above setup the first reminder should arrive approximately 15 min after the workflow was started... Am I right?

Thanks - I am aware of that option but for simple reminders I would like to use the flexi task functionality and just figure out why it is not working...

Igor - Have you confirmed that the regular Send Notification action works to send a basic email from Nintex (to the same person you are reminding and/or escalating to).

Assuming Send Notification works, so that we know Nintex is able to send out email, then I would test some other actions that are dependent on the timer service, such as Pause action (pause for 1 minute) or Wait for Item Update.  Maybe you need to start the Timer Service.

I get the initial task notification from the Flexi Task. The escalation also works approving the task automatically and then I get the response not required email and one "Send notification" email... That would suggest that both notifications and the timer job works as expected...

Being frustrated with this I restarted all servers and created a new workflow from scratch and it seems to be working now...