i've had a number of epic pieces over the years, i'm a pretty big fan, but they do have some drawbacks & limitations, like almost any piece of gear.
They need to be seam sealed to be truly useable, but once they are, they hold up rather well, they're breathable enough for be but i don't sweat much (aren't i so cool :p ), anyways, i like them for bad weather bushwacking a lot, as they're pretty tough & you don't have to reproof them all the time when you get them dirty, just give 'em a wash & the water repellency is back (use non-detergent soap), usually if it's warm enough that it's getting too hot in the epic, it's warm enough that the neglible amount of rain that'll come in from leaving it unzipped isn't a big deal. after having 2 patagonia epic jackets & a golite, i've just got the wildthings epic hooded windshirt & i love it, the material is thinner, the hood is *excellent* & it has nice inside pockets
another option to consider is the REI pyrn jacket, made of pertex equilibrium, $80,10oz. i just ordered one & will get back to the boards on how it performs, it's supposedly pretty weather resistant, so sayeth the backpacking light.com review staff i plan to use it as windshirt/midlayer combo, the reviews on this site say that the fabric is very windresistant & sheds a good bit of water, plus it's a bicomponent fabric that helps to keeps water moving away from your skin. for more ontrail type adventures i'll be using this & a hardshell, for more offtrail stuff were i need kit that'll perform over a wide range of conditions (while sacrificing suitability for certain specifics) i'll use my epic windshirt & pants. in colder conditions where 'wet' is a possibility, i'll also use my epic suit alone, but if conditions get bad, it'll mean you just need to keep moving to keep your heat up & you'll stay as dry as you're gonna, just have some insulation handy for when you stop.
with pretty much any piece of weather protection clothing you're gonna get wet some how, from inside (sweat), or from outside (leaking, not completely waterproof gear) it takes some experience to learn where the balance is between the two for your comfort range.
so to answer your questions, it's pretty breathable, a big plus is that it starts breathing from the get go, unlike goretex that takes some time to reach a critical moisture level before it starts breathing, if came to epic VS traditional waterproof/breathables, i'd go epic, i accidently got caught on my bike 25mi from home when a hurricane hit here in NC last summer, although the fabric seemed wetted-out to the touch i wasn't anymore wet inside than one would expect from riding a bike for 25mi (sweat) epic VS eVent, that's a different bag, for certain kinds of trips i'd take a more breathable windshirt & the event shell for backup, if that's not something you can afford, then definitely go for the epic, seam seal it & figure out how to use it best, it can get you far for not that much money & not that much weight (IMHO), remember that how you layer under it is important too.
the wild things gear epic hooded windshirt is a top-notch piece of gear, i highly recommned it.
i also highly recommend 'the science of breathability' article on this website, if you haven't already read it