personally I think its the best rule set GW have. It's designed more for smaller games, rather than HUGE battles, but it does scale well from just a few troops, up to about 40 or 50 on each side.
There's no waiting around forever for your turn, both players move in the movement phase, then both do shooting, and then the fights happen, so it plays a lot better than 40K and AoS.
If you can find someone to give you an intro game I would recommend it!