Probably the Pentium Extreme Edition series will have 4MB L2 cache while the Pentium D series will have 2MB L2 cache.
The Conroe processor is inspired by the Pentium M design and features a 14 pipeline stage design, with VT, EIST, EM64T and XD but no HT.
The chipset support isn't clear but currently it's believed only the 965 and 975 chipset from Intel will support the Conroe.
Source: VR-Zone.