Overall it is excellent, though I do not use all of it.
It comes with:
-a foldable paper battle mat with 1 inch squares
-cards that have a lot of frequently referenced rules for easy reference-1 card each for things like turn unded, grappling, overbear, bull rush, trip, etc. Very handy and better than a DM screen. Buy a cheap pack of laminating pouches form someplace like Wal Mart and you have easy reference and eliminate book flipping.
-cut out counters for spell area effects and common spell effects (lines, cones, bigby's hands, etc.) plus counters for hourses that can slide under a mini etc. Allow you to visualize and/or measure space these things take on the battlemat and measure effects to see who is affected by area spells
-a short book with some optional chase rules by Mike Mearls I think.
The thing I use the most are the reference cards, for me they are worth the cost of the product by themselves, and the rest is gravy.
-M