Yeah, it is a server OS. It is to Windows Server 2008 what Windows 7 is to Vista. It is just a server OS like Server 2003 or 2008, just more updated. Don't let the R2 confuse you, it just means Release 2.
As someone who has used Windows server operating systems in desktop use before, with previous Server releases it actually made a fair bit of sense, depending on your needs, because they were so naked and secure out of the box, and you could enable what you wanted or needed. However, some games or even apps did balk at it not being the Windows version they expected when trying to install, but in many cases that could be fixed by editing the MSI config file.
However, from what I have read about Server 2008 R2, whereas you could squeeze 2003 to run faster than XP, the difference in desktop use between Windows 7 and Server 2008 R2 is so negligible that it isn't worth the bother. Furthermore, S2008R2 lacked Bluetooth stack entirely last I heard.
Windows Server OSs are fun to mess around with in desktop use if you are into that sort of thing.