I admit I wasn't too sure about the comfort when I first received them since there is an elastic strip that keeps the inner tongue pulled in and with my very high-instep feet it took a while to get used to slipping them on. But now that I've worn them for riding >1000 miles I really like the comfort and figured out how to get them on with little effort. Soles are stiff enough for me. The pop-in/out feature of the Boa clasp is terrific. They run about true to size, if anything err on ordering a larger size. I haven't yet had the need to do a lot of walking or hike-a-biking in them, so jury is still out on that question.
I bought the MW501 shoes in size 45, the same size I wear in Shimano RX-800 gravel shoes. The MW701 were out of stock in my size but when they came back in stock I picked up a pair of those as well, so I can offer a direct comparison between the two shoes. The MW501 seem to be well made and are reasonably warm. While my RX-800s are a snug fit, the MW501s in the same size are roomier and allow for thicker socks. However the MW701s are even roomier, and I prefer them to the MW501s. If you want to pile on thick socks or multiple pairs of socks with the MW501 you might want to go up one size from your regular Shimano shoes size. On the other hand if I wear thin socks with the MW701 they almost feel too big. So the MW501 is going to work best for me with medium thickness wool socks for days where it is cool (40deg F +/-) and the MW701 are going to be the go-to when it gets close to freezing or below. Once it gets below freezing my toes are only good for an hour in either shoe unless I add chemical toe warmers, and the extra room in the MW701s allows me to add those without getting too tight.
Purchased the Shimano SH-RX800 on recommendation from biketiresdirect.
Fit nice and snug when I first put them on. Initial rides were on the trainer and I didn't like the shoes too much. I experienced some pain on the top of my foot and thought about returning the shoes.
On my first ride outside on the bike the shoes felt a whole lot better. Since then I have not had any additional issues with the shoes on rides from an hour to 2.5 hrs.
From my experience, I had to suffer through a short uncomfortable period of breaking in the shoes. That being said I am happy now that the shoes have softened up but still fit snug and provide a stiff sole for pedaling efficiency.
It's a nice replacement from the older Specialized MTB Pro shoes that I had used forever.