I'm administrating TimeMachine for my employer. It sucks so incredibly hard on a lot of points:
1) it requires the aged AFP protocol instead of Samba
2) No user-/machine-defineable quota, only one across the whole server
3) Extremely poor behavior in higher-than-10ms-latency scenarios
4) no way of scripting the configuration if one wants encryption of the backup image
5) Audits/reporting? Forget about it.
6) All backup images end up in one directory on the server, no way to specify e.g. the user's home directory
7) Restore takes ages