If your main machine is a laptop, do NOT run Server on it.
I tried this once, and was rather taken aback by the amount of time it spent with the fans on full. The battery life was cut by at least 50%, too.
Most of this is down to such abominations as PostgreSQL, which seems to love the CPU and makes as much use of it as possible.
I have since installed it on my Mac Mini at home, and it too spends its time with the fan running more than it used to. However, it has less of an impact on a machine that is always connected to a power outlet.
One problem I have found with the OS X Server app is that after it has been updated a few times, it needs deleting and reinstalling again, to make PostgreSQL work at all. Without doing this, it just sits filling the log with messages about PostgreSQL not being started, and has a Python process eating CPU all the time (presumably looking for PostgreSQL?). The remedy is fairly simple - delete the Server app and wait for it to notice and tell you. Then install it afresh, and it's OK again. For a while.
Having said all this, once it's set up and working, the Caching service, the Time Machine service, the VPN service and the Xcode service with its Git server - are all wonderful.