I thought Id share my experience of setting up a Mac Mini Server which I am using as a normal machine and have had no intention of using as a server. Ever!
As explained earlier on this thread, I simply want to use the machine as a home data dump mainly (with several iOS devices and 3 kids, we generate a lot of data, photos, video & music) but the quad core i7 processor and the double capacity 7200rpm HDD were also significant attractions. I am not a gamer so discrete GPU was not an issue for me.
In the main, setting up is relatively easy BUY there's a couple of tricky steps which I managed to overcome using some of the excellent advice offered on these boards by other users as well as that especially of @cphbite (with thanks).
The first tricky step for those with wireless keyboards and touchpads/mouse, there is no simple way to get the machine to pair up before set up. Catch 22 situation although some people have found unpairing the keyboards (if they had previously been paired with iPads) and several re-boots eventually worked. In the real world (with kids and other calls on your time), I borrowed a USB keyboard and mouse and completed the set up with those.
Another stumbling block for those familiar with good old 'Setup' assistant if you have it before setting up other non-server Macs. Well this doesnt work on Lion Server, because it searches for other servers that you may want migrating first. So you have to set up the machine first (and the option given to you is setting up a new Server). Dont let that bother you. Click continue and you can migrate your user data after you set up.
So the final and main tricky bit. You are asked to name the computer (easy) and also give a server host name (well, you do need to know what you are doing here and Apple Care will not immediately give you the right answer on this step because they dont know themselves. And you probably have to be put through a couple of people until you reach enterprise team). In fact, I was told by the retail team Apple care representative that I probably should have taken the Mac Mini retail instead of server. A momentary weakness there made me think that perhaps I had bitten more than I can chew! But then I remembered another members advice setting up and I tried out inputting his suggested root of for example (home-vault.com). It may well be that you have to use www.home-vault.home-vault.com at another place but I didnt have to use that.
Finally once you are set up you can then pair your wireless keyboard and trackpad in System Preferences (press the Apple sign on the top left).
There was another place where IP address needed to be inputted, I didnt have to deal with that because the machine populated those inputs. There was a place where I had to push through and get to where you set up connections (so that I could join my wireless network) and then push back in the process to get me to other inputs.