I store users' roaming profiles and home directories on a server running Windows SBS 2003. The server's storage is a SATA RAID-5 (3ware rocks!). SBS backs itself up to disk weekly, which I occasionally transfer to an external hard drive for DR purposes. The profile and home directories are separate SMB shares because the share containing the roaming profiles is configured to disallow client-side caching (which causes problems with the user profile loader on older versions of Windows and maybe even Vista). The shares are accessed via MSDfs because some day I'd like to replicate them to a second server and want any accesses or fail-over to be somewhat automatic (again, for DR purposes). I use Group Policy to move each user's "AppData", "Contacts", "Desktop", "Documents", "Downloads", "Favorites", "Links", "Saved Games", and "Searches" folders to their home directory. In my scheme, "Music", "Pictures", and "Videos" are sub-folders of "Documents", for backwards compatibility with Windows XP. I've also configured Volume Shadow Copy, which allows users to retrieve older versions of their files without needing to bother me about restoring them from archival backups, and deployed Certificate Services on SBS. Each user's enrolled in the domain PKI, so they can encrypt their caches as well as any of their files.
From the users' perspective, everything is automatic: They log in, work with their files, and log out. If they are out of the office, they'll get a warning about working with a cached copy of their profile, but that's about it. When they return, they'll get prompted to sync any conflicting changes made while offline. Windows has featured CSC (also known as "Offline Files") for some time, but it's only gotten really stable in Windows Vista. A few programs don't really play well with CSC but nothing that's a deal-breaker (like Firefox or Skype storing database stuff in the roaming version of the AppData folder when it really should be in local version instead, but I kind of brought that on myself when I redirected it to the network share to start with).