Had a crack at it a little while ago but got sucked back in to Hearthstone instead before it got a chance to grab hold.
For those of you who have played MOBAs, it's much the same bar a few small difference.
1) There are no items. Instead, when Heroes level in round, they can pick an upgrade that adds a small bonus. More and more of these upgrades get unlocked as you gain heroes levels out of game.
2) The maps have random quirks in the form of alternate objectives. For instance, the pirate map has you charging around smashing open chests for gold. First team to hit a certain amount, then return to the pirate captain gets a buff as the captain bombs the opposing teams fortifications with cannons.
3) Everyone gets mounts. You move slightly faster but can't use abilities. It is a little jarring to see Jim Raynor riding a horse though.
4) The whole thing is very tongue in cheek and if you've grown up with Blizzard canon, you're going to love it for the fan service or you're going to find it very jarring for the complete disregard of logic or reasonable explanation. There is a vague premise of a magical "Nexus" summoning Heroes from across the "multiverse" to do battle for unclarified reasons. But when Raynor asks if the Nexus is a Protoss Nexus, Uther's response is "Don't think about it too hard." That pretty much sums up the game's attitude to fluff in a nutshell.