User Voice - Is it worth adding ideas or is it a waste of time?

For me the answer is 'it depends'.

If it's something major, and it's a feature/function likely to impact most/many of Nintex's clients then I'll suggest it on UserVoice/Product Feature Request (as it's called on the More Resources menu on this page). 
Yes, some things have taken much longer than expected to be released (have been waiting for the process reporting API for about 4 years).
I do think it's worth letting Nintex know features that you'd like to see though; they do read the suggestions.

Eddie – first and foremost, thanks very much for sharing your perspective.  We know that when a customer provides a suggestion via UserVoice or even in a forum such as NCC, they are doing it from a place of wanting to make the product they use every day better (which is our main goal as well!). 

Customer feedback is one of the many inputs we have in the product planning process; we hear your feedback and recognize that it can sometimes feel like the responses to suggestions don’t come as frequently as customers may anticipate.  Starting at the beginning of this year we’ve adopted a new strategy around UserVoice suggestions to be more transparent with customers by implementing timeframes by which each suggestion can sit in each status.

A status is the frame that we use within Nintex Product Management to organize and move suggestions or ideas through UserVoice; some example statuses that you may see are: Already Exists, Under Review, Planned, Completed, Not Planned and others.  Our intent here is to provide more transparency around our planning process so that customers like yourself can better understand if we are going to act on their suggestion and if so, when.

We appreciate your patience as we work through the rollout of this new approach and our hope is that it over time you will gain more clarity on the features that we are planning on shipping and continue to feel confident in the feedback you provide.

Thanks very much!