Technically Duron 850 is nothing particularly exciting. It is using the same core as previous Duron at 600-800 MHz, it runs at the same 1.6 V and it has the same processor bus clock of 100 MHz or 200 MHz DDR. There is nothing wrong with that, because Duron has been an excellent performer since its release in June 2000 and at 850 MHz it will continue to easily beat any competitor in the low-cost segment and even some in higher segments as well. Intel's Celeron has never been a match for Duron in the past, and Intel's desperate but late switch to the 100 MHz Celeron processor bus doesn't make any difference whatsoever.
Duron 850 is also sharing the bad sides with its predecessors. It produces a lot more heat than Intel's Celeron or Pentium III processors and it is also lacking a thermal protection. The latter can easily lead to a sudden heat-death of Duron, in case the heat sink was not mounted properly or the heat sink's fan should cease to work. Besides that Duron used to suffer from the fact that it was requiring the same SocketA-platforms as Athlon, which happened to be targeted to the high-end segment, making them rather expensive. Now there's finally two low-cost chipsets with integrated 3D-graphics available for Duron as well, VIA's Apollo KM133 and SiS's 730 chipsets. These two new platforms will ensure the production of extremely inexpensive Duron systems.