This list is constructed out of responses from this mailing list thread regarding "Why Are You NOT Using FreeBSD?"
- Exchange (MAPI) and its groupware functionality missing.
- Telephony (ISDN to SIP gateways, Asterisk etc) missing.
- FreeBSD in the mobile space isn't too good.
- No Gluster file-system support.
- It doesn't yet support the latest graphics drivers (except for the NVIDIA binary driver, but the ATI and Intel drivers for FreeBSD are ages behind).
- The lack of suspend-and-resume for laptops.
- Incomplete ISDN support.
- Broken ports packages.
- It's easier to run Mac OS X than FreeBSD.