It's too early to make a call on the RADEON 9100. There aren't any systems sporting the chipset which have been released yet; and according to ATI, the chipset hasn't even been finalized. The situation is certainly a promising one, though. ATI has an undeniable leg up on Intel's 865G chipset in the 3D performance corner, and with a little more optimization the RADEON 9100 IGP could just be able to take the crown in office productivity too.
If the chipset were to have one notable flaw, it would be the IXP 250 southbridge. Without native support for Serial ATA, motherboard manufacturers are footing the bill to integrate a third-party controller, invariably influencing costs to consumers. Incorporating support within the 9100 IGP for third-party southbridges is a helpful solution, but connecting through the PCI bus is certainly a limitation any way you look at it. Realistically, an up-to-date version of the IXP can't come soon enough.