I just recently went and caught up on Green Lantern Rebirth and (still)
catching up on the rest of the GL stuff.  GL: Rebirth impressed the HELL outta me, but I gotta say, I was sold on this book when
the art for this cover was released online – easily my favorite cover since Michael Turner’s Civil War 3 variant.   My extent
of Flash knowledge comes solely from Crisis On Infinite Earths and New
Frontier (the same went for Green Lantern before I actually dove in). 
I was so pumped to check this out, and just as Johns (and Van Sciver)
sold me on GL with Rebirth (I’m determined to catch up on both GL and Corps before Blackest Night), it looks like they’ll be doing the same
here.  No knowledge is needed about the character (as was the case with GL: R) and by the end of the issue, you CARE.  That’s no small feat.  Solid writing, amazing art, put simply, this is just a GOOD COMIC. SOLID. You even get an understanding of the somewhat convoluted nature of the other Flashes, as Johns uses the same magic touch he had in seamlessly explaining Paralax and associated backstory for GL.  What more can you ask for?