I have many friends that have purchased De Niro boots over the past couple of years. Some of them have multiple pairs - a show boot, a clinic boot, a barn boot, etc. At least one person has several pairs of show boots - a blue pair and a black pair, to match her shadbelly and short coat.
The overall consensus seems to be that you can’t beat the comfort, or the good looks, but to not expect a lot of longevity. They tend to break down around the ankles, and the brushed leather in particular gets rubs and abrasions very easily, that do not buff out.
The fit can also be tricky - most of the people I know have used a master fitter, but for some, their boots did not fit at all when they arrived and had to be sent back. And lead times for customs can be quite lengthy, esp. since the boots are handmade in Italy. One person waited over five months (and hers didn’t fit). It is my understanding that the De Niros have become so popular, that the factory in Italy was overwhelmed trying to keep up with orders.
The upside is that the leather quality and workmanship are usually very, very good, and since the De Niros are fully customizable, you can pretty much design exactly what you want - the choices for style, leather type, color, trim, bling, etc., are mind-boggling. I have seen some stunningly gorgeous boots at some of their trunk shows.