The product has been very useful so far; it's easy of use, powerful enough but still user friendly! It could be better if there were more templates available or different ones (I would like some "standard" emails).
I have not found any specific issue that makes me dislike this solution at present time - everything seems fine as such with mailNEST being used by my team within our organization since last year now. And we are happy about its performance too!! We're solving issues related mostly around internal communication between employees via mails which had previously caused delays before reaching their destination due external factors/problems outside your control when sending them out from other than work computers etc..