When I set up our 2003 SBS server a friend who has been working sysadmin for quite a while told me WSUS was "a must for any size of organization". So I installed it, and have been using it since.
However, I'm beginning to feel that it might be a bit overkill. Our company has five workstations, one laptop and one server. I barely ever block updates (happend once IIRC, and "extra games for Vista" type of update...). Also making sure the laptop is updated - which is almost only used when someone is on a trip, or giving a presentation at a customer - is a pain, since it is very seldom connected to the office network, neither physically or over VPN.
Do you see any point in me keeping WSUS?