OpenSolaris supports a variety of SPARC and x86 platforms. AMD 32-bit and 64-bit, Intel 32 and 64-bit Pentium and Core2 architectures are supported in the x86 space. Sun SPARC platforms provided a 64-bit architecture long before 64-bit was available in the x86 space. This meant that 64-bit support has been present and has evolved in Solaris over a significant amount of time before the birth of OpenSolaris. OpenSolaris comes with both 32- and 64-bit kernels, and runs the 64-bit kernel by default on 64-bit hardware. However, the operating environment is not exclusively 64-bit even in 64-bit mode. Most user-space utilities and applications are still 32-bit apps, but they run transparently with a 64-bit kernel. Only utilities that need 54-bit support are compiled as such; for example, Xorg, process management tools, etc.
Refe, /software/solaris(faqs/64bit.xml for some useful information in this regard.
Prior to OpenSolaris, device support in Solaris for x86 hardware was very limited mainly due to the fact that support for Solaris on the x86 platform was dropped for some time in the Solaris 9 time frame. However, from Solaris 10, and especially after OpenSolaris, there has been a big push to support x86 hardware, resulting in a drastic device support improvement in OpenSolaris. You will find that OpenSolaris supports most x86 hardware very well. When in doubt, it is wise to check out the hardware compatibility list at http:/bigadmin/hcl/. Booting one of the LiveCDs (Indiana or BeleniX) is also a good test. However, OpenSolaris does not yet support infrared, Bluetooth and fingerprint reader devices.