Sizing:
Short version: I'd recommend trying a half size below your running shoe size(e.g. size 11 running, get size 10.5 in these).  Then if your feet are wide in some of your shoes, get wide (EE).  The leather will break in on tight shoes, but not the steel toe.

Long version: Sizing with Ariat boots I've found to be very tricky, and that's probably my only complaint with these boots or the company.  In short, I've found all Ariat boot styles to fit slightly differently.  On a trip to Nashville I tried on numerous pairs of Ariat boots and from everything from a 9-EE (wde) to a 11.5-R (regular) to fit me well.  In my other steel toe boots, Belleville 550 ST (combat style opposed to western) I wear a 10.5-R.  Typically in shoes that run narrow, I need wide shoes.  My feet are wide, but not so wide that I always need wide footwear.  Based on my experience with the sizing and what I'd put on, I tried an 11-EE in these first (same as my running shoe size), which was slightly too big.  Ariat's description of how to fit them reads:

"When you slide your foot into a boot, use either boot pulls to pull it on while sitting, or stand up in to the boots. A well-fitting boot should fit your heel snugly. Expect a small amount of movement (lift) in the heel as you walk, because a boot that fits properly should flex as you walk, and your heel should lift a little, but not too much. New boots will have a stiffer sole. As you break in the boot, the sole will flex to a comfortable level and most slippage should stop."

I found this to be a bit misleading.  There was about 5mm extra room with my thumb on the toe of the sole in front of my foot, and my heel lifted from the boot slightly as I walked.  I felt like that matched their description, but it didn't feel right.  It seemed loose.  So I ordered a pair a size down (10.5-EE) and it was a perfect fit.  So in summation, I found that the best fit was to match the same size as my other steel toe boots and go with wide.  Leather will break in so you want them to be pretty snug when you first wear them  The steel toe won't however, so if it's hurting your toes or pinching them on the sides at the steel toe, you need to try a larger size.

Quality -Initial:
I will update this review when I've had more time to wear the boots and get a feel for how they hold up.  That said, my initial impression is high.  The boots are very comfortable, once you're in the right size, and feel great.  The sole is much nicer than most boots I've owned.  They go into detail on the purpose of each layer (see the Ariat ATS Max photo in the product description).  At this point I'm confident that the slight aeration to the soles will help pull away moisture so that it doesn't feel like your standing in a puddle after slight to moderate sweating.  The arch support is also good, a problem I usually have with other shoes and need to buy my own inserts.  It's not so extreme that I think people with flatter feet than mine will have issue but enough that it's comfortable even with my higher arches.  With work socks on the material had the right amount of friction that it doesn't slide nor stick so much that it irritates my feet or is hard to remove, perfect amount of grip.  The steel toe is great, and I barely notice it.  I've had other western style boots where the steel toe was sort of wedged and it was very uncomfortable on my big toe.  No such issue here.  These are honestly some of the most comfortable boots I've owned out of the box.  I won't need to break these in as much as other's I've owned.

The material on the outside is as nice and as of high a level of workmanship as the photos and what you would expect from Ariat.  Stitching and leather are superb.  Honestly the quality of these boots is high enough that they're great for work in rough environments or even as nice boots for wearing out if kept clean.

Cons: Price is high, although it is worth it.  Sizing is tricky, but once you have that down it's a great fit.

These boots met and exceeded my expectations.  I typically am not one to give 5 stars unless I'm truly impressed with the product and have no critique.  I would dock it 0.5 stars for difficulty with sizing and price, but not worth docking a whole star.