Simply put, Linux runs on more platforms than any other server OS available. The 2.4 kernel includes support for 13 different processor families (if you count MIPS, MIPS64, SPARC, and UltraSPARC as four separate families)from the largest of the large, IBM's S/390, to the smallest of the small, the Intel StrongARM and the Hitachi SuperH (found in many handheld/PDA devices). While this doesn't affect Linux setups you already have in production, it may have bearing on your future Linux strategy. For example, management at my current company has expressed interest in redeploying PowerPC and SPARCbased hardware (formally running AIX and Solaris, respectively) with Linux to leverage the x86 Linux skillset pool available. If you've ever tried to build a staff of senior-level techs, all conversant in three or four dialects of UNIX, you can understand why running a single operating system on all platforms is attractive.
For existing Linux deployments, optimizations are available, as well as large memory support (up to 64GB), and much better SMP support. The optimizations come in the form of explicit support for a large variety of x86-compatible processors, including MMTR (Memory Type Range Register) support, which speeds up PCI and AGP bus write bursts, and a feature to update Intel processor microcode. The new and improved APM (Advanced Power Management) standard, APCI (Advanced Configuration and Power Interface), is now supported for motherboards with this feature. Linux 2.4 has support for more IDE chipsets, allowing chipset-specific tuning and performance enhancements so that you can eke out better disk performance from your disk subsystem.