I've donated plenty towards Pinco's UI in the past and I've been an advocate of his UI since I started using it. You won't find a bigger promoter (except for Pinco himself of course.) I've used it up until recently, resorting to making my own UI since the only two options for user interfaces are buggy.
With that being said... there are bugs in the default UI, there are bugs in Pinco's UI, you can see these bugs clearly by typing /debugwindow, clicking on Show Options, enabling all types of logging, then check Enable Logging and go run around a bit. It has been this way for over 6 months. These are not new bugs, these are old bugs that have been reported and discussed. The bugs that the log catches are actually easy to fix, but there are also bugs that don't show up in the log.
As far as the default UI, Pinco is not the one to blame. He obviously wasn't paid to keep the default UI updated and/or is not on the payroll.
As far as Pinco's UI, I honestly think he just lost interest in it. These bugs existed for over 6 months, while the project health status was still healthy. The donations started as something to get people to post new ideas and donate towards getting them added. I stopped donating because bugs stopped getting fixed.