One Page Rules gives you yet another option for your miniatures gaming needs. They have updated their rules sets to bring you new units that have been coming out that had not yet been represented in their games. One Page 40k got the biggest update of the bunch, bringing you several new units, as well as making a new army all on their own. Several other units also got a bit of a balancing.
In terms of the new army, that would be the Harlequins. They're no longer part of the Eldar army list, but are one on their own. All of the new units have also been added to the roster. Tyranids also got a bit of a bump in force numbers, with 5 new additions.
General changes include things like vehicles only rolling once on the damage table, even if they take multiple wounds at once, a rewording of Waagh! for the Orks, Space Marine Captains gain Tactics and their Chaplains now have Tough. Taking a trip over to the Fantasy side, Vampire Counts had their Blood Knights point cost fixed.