I would say this is slightly dependent on your audience. I design a lot of things for Joe Public who has little to no experience with my product, or new technology as a whole, and therefore can be intimidated easily.
Joe is using the site I built because his employer told him to. Joe still has the morning paper delivered to his doorstep rather than his inbox. He gets frustrated when he comes home and wants to watch TV but it's on HDMI2 from his son playing Xbox and he has no clue how to get the game on. The last thing Joe needs is my product, some new, complicated piece of technology, telling him he's wrong and making mistakes.
Now, I'd like to think that everyone has thick enough skin to handle a simple error message, but for those who don't want to be using the site, negative error messages only reassure their negative feelings. It's been my rule of thumb to not use "error" messages, but use "help" messages. As cheesy as that sounds, I find I get a much better response when something goes wrong and I need to provide technical support.
Take your example of:
'failed to complete registration, please see below for invalid field entries'
Depending on the nature of your form, you could make it a more light-hearted message, something like:
Oops! You missed a spot. Don't worry, we've highlighted it so you don't have to guess where.
Or for a more professional approach, something like:
Please complete the highlighted fields in order to continue.
Basically, if your user base is similar to mine, you'll want to "be nice" to them. You're most likely not going to offend someone by using a negative error message, but with positive messages, I think you'll find that those who are weary of your product will become more comfortable and less willing to give up at the sight of an error.