Thanks for the review. I'm currently awaiting delivery of my Nextion screen but in the meantime have built my interface with their Nextion Editor. In comparison to other HMI offerings in this price bracket, I've found the Nextion editor on par with ease of use, albeit the documentation is relatively poor and the best learning resource are user contributed projects in their forums. I'm really hoping that the colour reproduction and view angles aren't as bad as you suggest...
For my particular application I want a HMI that will respond to several digital inputs and potentially transmit data to other devices by serial. The Nextion has the advantage that it can do this out of the box (albeit I will add some power regulation and optically isolate the digital inputs) without an additional MCU. Other offerings like 4D Systems or MikroElektronica's MikroMedia are substantially more expensive. If my project was a one of I'd investigate the MikroMedia displays, however as I'm developing a low volume consumer product the higher cost of those would eliminate any possibility of making a profit!