I've tried this on in the New Balance store, but haven't worn it outside.

The fit of the last (foot shape) is identical to the MT20, which I find a tad tighter in the toes than the MT10 due to a slightly more pointed last. The upper has a similar amount of volume in the toes as the MT20 but uses an even stiffer mesh that has less give than the mesh of the MT20. This no doubt helps to keep out dust/sand and protect from puddles, but I found it tends to fold and bunch up a little around the flex point for me but it will probably soften with use. The tongue is not gusseted and I found it easily twisted and folded when putting the foot in. I didn't like this part very much, and don't understand why a trail shoe wouldn't have a gusseted tongue.

Length is true to size barefoot or with a thin sock. However, I found the toe-room a bit lacking compared to the mesh covered MT10 due to the stiffer upper and the slightly more pointed toe, and even a wide (2EE) in my measured size (10.5) allowed my 4th and 5th toes to rub the end of the shoe. In the end I needed to go up a half size to the 11D in the MO80 to accomodate my wide toe splay and might need and 11 EE even though the shoe was a tad long for me in that length. Not ideal, and I'm a bit disappointed that New Balance used a narrower toe on this model.

The MO80 has good forefoot flex but is definitely much stiffer then the MT10/20 (particularly in the mid-foot and heel), though not as stiff as the MT110. The midsole is a beefed up MT10/20 with amazing toothy tread. It is a bit less cushioned than the MT110, especially in the forefoot. The vibram outsole is soft and will probably wear fast on rock and asphalt but is great for trails. The lugs will probably make it uncomfortable on paved roads anyway.

Lastly - there is a pronounced arch support in these compared to the MT10/20. That might be a good or bad thing depending on your needs. True minimalists will probably find it far too much, while bad over-pronators like myself transitioning to minimalist running will appreciate the support. I couldn't keep the MT110s due to lack of any arch support and the raised lateral edge increasing my over-pronation.

Overall a good shoe, but I wish it had a little more midsole in the forefoot and a more rounded toe like the MT10. The level of midsole support is a bit light for people transitioning or logging a lot of hard miles on technical terrain, and the stiffer heel/midfoot and arch support might encourage a heel strike in those still learning proper barefoot form. I'd give it 3.5 out of 5 stars.