I purchased these shoes as well as the innov-8 x-talon 212's for use in two Spartan Sprints (with more to come) as well as trail running/training.  I have no doubt that the Speedcross 3's are a great shoe for mud runs but I ended up returning these for reasons I'll get to momentarily.

I did not try these shoes out on any runs so I cannot vouch for their performance on trails but here are my thoughts based on my limited time with them.

PROs
- The shoes hug your feet quite comfortably and seem very secure. I felt like my feet were protected from anything and everything with these on.
- Grip is top notch.  The cleats on the sole are deep and clearly made to grip and release mud, dirt or whatever you run through.
- Lightweight. For a big shoe (mid-top/high-top shoe) this is surprisingly light.

CONs
- Maximum cushioning.  Tons of cushioning on this to the point that you probably gain an inch or so of height wearing them, like wearing a pair of hi-top basketball shoes.  No way you will feel any rocks or branches when running these on the trails.  Some may take this as a pro and, if so, this shoe is for you.  If you like to have a bit more feel on your trail runs then this is not the shoe for you.
- Thick shoes all around.  All parts of this shoe seem thick and substantial.  You feel secure in the shoe but these are not the type of shoes that disappear on your feet when you put them on.  The Speedcross 3's are basically the anti-minimalist shoe.

There are many good points to the Speedcross and I would bet that for someone running long distance trails this is a perfect shoe.  I prefer a bit more feel when trail running, not minimalist per se but definitely towards that end of the cushioning spectrum.

If you want a shoe that can take you through multiple mud runs and fight through mud, rocks and debris without your feet feeling a thing, this shoe is for you.  If you prefer a less is more approach to your shoes, try something else like the innov-8 x-talon 212s.

Overall: 4/5 I considered giving this 3 stars but the shoe is top quality and is a great cushioned shoe for trails, it just didn't fit my particular needs.