I can't believe some of you complaining...
Haven't you ever played games without 360 degree shooting? I'll admit I'm only playing on hero mode, haven't tried the hardest, but I've had <no> trouble progressing through the game despite having to use a laptop touchpad (it makes it a little trickier, but still bearable). Don't want to miss? Move your character so the bullets hit properly, that's the whole point of this game, you can't just stand in one spot and expect to blast them in every direction.
As far as the guy complaining about kiting, we're obviously not playing the same game, it's entirely possible to kite them around: the whole object is to keep grabbing the gun upgrades, once you have one, fight your way to the next and wait until your current one runs out until you grab it, you'll very rarely find yourself fighting with the basic gun, when you are just dance around them on the very edges of the mob. Use the terrain to your advantage, it's very easy to get over half the zombies stuck behind buildings, or to fight only a couple at a time when you're in a narrow doorway.. they CAN'T walk over one another after all, that should be your main strategy in and of itself taking that into consideration. Once you get to the levels with grenades (which you use separately form guns) as well it becomes quite easy to crowd control them.
I'm not a great gamer and I'm certainly not trying to claim that I am, most of the people on this site are probably a lot better than me, but this is a pretty straightforward game that is both quite fun and involves some but not a lot of thinking, mainly memorizing obstacles on the field, but is entirely fun to play as it is. The inclusion of 360 degree shooting would ruin the main aspect of what makes it fun: it's difficulty is in kiting them nonstop and not just aiming your gun to shoot them, but moving your character so the shots connect as well. If like some reviews suggest you could just stand there firing in every direction and had some much more powerful gun nonstop the little strategy and difficulty in this game would disapear.
I congratulate the author not only for the game but for the gameplay mechanics, unfortunately some of your player base doesn't want to bother to spend more than 2-3 minutes figuring it out and instead insists on saying things that are completely untrue such as it being "unplayable". I personally hope you don't change it, as I feel it would really ruin the main basis of what makes this fun, and difficult, and not just another automatic kill fest with no challenge to it.