Just saying it now, melee is retuned. You can't endlessly power attack any more. The best way to play is to use left click attack to get a stagger (left click is buffed some). Then power attack, as power attacking against a knocked down opponent does extra damage. I mean sure you can go flying in there and power attack sometimes, but you want to try and save it until they are knocked down and then you get the kill most of the time.
Another nice strategy is to get a sneak bow shot for 2x damage, then you can usually power attack for a kill or knockdown.
Before left click was pretty useless. Now left click is good for mining too. You can power attack mine, but its pretty dumb considering its meant for melee combat. Like anything try it out, and experiment you'll find your groove. It plays how we intended now, with primary attacks being good, and power attacks more used in situations where it makes sense because if you run out of stamina you are screwed. It also is set up for a risk reward style of play because you WANT to get that power shot kill in but sometimes other zombies are near so its a little risky.
Firearms have way more up front damage and less perked late game damage. (They are still really nice) So they are now useful early game, 2 head shots instead of 7 to kill a weak zombie with a pistol, much better.
Anyhow a new patch is coming soon and its really awesome. I overhauled trader prices and economy so theres mods at traders now and way more accessible brown guns but the price skyrockets as the quality gets good. They have more construction materials and all the new foods are possible to spawn, vending machines have the new foods too.
A ton of stuff coming. Its playing really good. Some nice optimizations too, with a big one coming at some point.