The FreeBSD Project describes Version 5.1 as a "new technology" release, intended to enable users to check out new features, such as Version 5.1's expanded support for USB (Universal Serial Bus) 2.0 devices, RAID and serial-ATA controllers, and USB Ethernet adapters.

For production settings, however, the older 4.8 release (the most recent "stable" FreeBSD edition) offers better stability, particularly in areas such as SMP (symmetric multiprocessing) support. SMP support in FreeBSD was reworked in Version 5.0 to improve scalability by allowing multiple threads to run concurrently in the kernel, and these facilities are not yet as mature as those in Version 4.8.

FreeBSD 4.8 might also offer better performance, due in part to the debugging code contained in 5.1 for testing purposes. Pending further testing, the FreeBSD Project plans to begin a stable 5.x branch—possibly as soon as this fall—when 5.x should be considered ready for critical production deployments.

FreeBSD includes a security utility that can minimize the damage caused by an attack on a service such as BIND (Berkeley Internet Name Domain) or sendmail by running the service within an isolated environment, or jail. FreeBSD 5.1 ships with new applications for managing these jails, including tools to list and run commands within existing jails.

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