The Open D tuning has been around for well over a century. One of the more famous pieces of the 19th century was Henry Worrall's Open D piece called "Sebastopol". Because of the popularity of this piece during that time, the tuning itself became known as the "Sebastapol" or "Vestapol" tuning.
Because of its relatively limited fretting requirements, open D is one of the simpler tunings to use on the guitar. The advantages of playing in open D are many. You can play the usual tonic chord, D major, by simply playing all the open strings. Other useful chords can be played by simply adding one or two fingers, or by barring across all the strings at particular fret positions. You can fret melodies on a single string while playing harmony notes on the open strings. These features is what made this tuning popular with blues guitarists, especially when playing slide guitar. The ability to produce a major chord without fretting any strings, and producing other major chords by laying the slide staright across the frets offerred obvious advantages to slide players.
The drawbacks are that the chord and scale positions are different from standard tuning, requiring you to familiarize yourself with new fret positions. The biggest drawback is that in an open tuning it may not always be as easy to play in keys other than the key of the tuning -- D major in the case of open D tuning. But of course, this drawback is what provides its biggest advantage; its much easier to play music in the key of D major.