Altra Instinct Shoe Review

My new Altra Instinct shoes arrived Thursday evening. I've been wanting a pair of Altra shoes for a while now. Their whole line of shoes are zero-drop and don't have all the crazy extra features that many shoes are hyped with--just shoes that let your foot act naturally, but still be protected.  I ran in them Friday (5 miles), Saturday (10 miles), and Sunday (5 miles). The runs were a combination of groomed trails and asphalt bike path. I need to test them on a treadmill and on a road run, but this will have to do for now. It's still early, but here are my first impressions:

• The shoes run small. I originally tried my normal size 13s and they were tight. I went with 14s and they are slightly big, but OK.
• The forefoot and toebox are nice and wide. Toes aren't squeezed.
• Zero drop (heel to toe) is great. Promotes natural forefoot landing.
• Thick midsole (~18mm with insole) is protective and provides firm cushioning, but it is very isolating--can't feel the ground. 
• They are a bit stiff--I prefer a more flexible shoe. Maybe that's the trade-off for extra protection and cushioning.
• The shoe is rather heavy (~11.3oz for my size 14 with insole). Definitely not a minimalist trainer. I need a more substantial shoe for my ultramarathons and this may be the right shoe for 30+ trail runs and races. 

I'll continue to use them through this fall and winter and will test them in a few ultramarathons starting in January. A more comprehensive shoe review will follow. My main "early season" race is a 50-miler in April.  If they get me through that race feeling good, I'll consider them a success. I don't see them being my daily trainer (I prefer more minimalist shoes for everyday runs), but they could be my new "go-to" shoe for marathons and ultras.