I've been using the Inov-8 X-Talon 212s for 6 months now as a trail running show for use in training across Salisbury Plain and as my race shoe for both Tough Mudder and Spartan series races. After researching before Tough Mudder in May 2012, I found several blogs and reviews from people who had run it before recommending either Inov-8s or Vibrams. When looking at the course structure, I decided to go for the X-Talon 212s as they seemed to have far superior grip and the majority of running would be through thick mud or wet grass fields.
I have been blown away at how good these shoes are off-road. The rubber grips are very sticky which is perfect for running on wet wood surfaces which you regularly have to in these races and during all of my training and races I have not slipped once in them. Even when running down wet, muddy hills racing in Spartan races and through the mile of mud at Tough Mudder, I was able to stay stable, fast and agile whilst others around me looked like Bambi on Ice!
They are very lightweight which helps not only with manoeuvrability but also by drying out very quickly after being soaked. They are also comfortable to swim in when traversing lakes and rivers- My old Asics would feel like bricks once they were soaked. The laces have rubber in them which helps them keep grip and they very rarely come undone. After 6 months of use they are still in very good condition with no rips, tears or marks. I've thrown them in the washing machine several times and each time they've come out looking like new.
These are minimalist shoes, so if you're not used to running in a minimalist shoe you should take precautions to both bed them and your feet in correctly. Using a traditional running technique that you would use with cushioned trainers can result in some pretty nasty injuries. There is loads of advice about this on the Internet and through your doctor- I found this link particularly useful. As with everything on this blog I'm no expert, I'm just listing what I did. Take professional advice if you feel you need it!
The only negative is that they are awful on hard surfaces- even chalk or flint. If it's not soft ground, you really feel it through your feet. They're not designed for hard surfaces, so this shouldn't be a surprise. They also aren't very handy on the balance beam obstacles that you sometimes get, due to how high the rubber studs are as they can send you off balance easily.
All in all, they have been fantastic.