Picked up a copy of Armored Core V during my lunch break. My first AC game!
I haven't played that particular entry. But I love the series. If you like customization in your war-machines, you'll love the game.
It's made by the same people that made the King's Field series and Demon/Dark Souls series; From Software.
It's strange, because the series has actually been on my radar for a looooong time, and I think I may have rented AC1 or 2 way back when, but the constant pace of new games, especially during the PS2 years, always put me off a little. Not in the sense of diminishing quality so much as not knowing where the hell to start.
I had tried a demo of 4 on 360 awhile back, but the mechs felt too loose in their movements, and everything looked so small that I had trouble seeing. This one, at least from the videos I've watched, seems a bit more MechWarrior 2'ish, and that is a VERY good thing.