Over the past couple of years I've done most of my road running in the Saucony Kinvara, Brooks Pure Flow and Pure Connect, and Altra Instinct. I've taken all of those shoes off road at some point, and with the exception of the Altra Instinct, I've found that they don't work so well on trails unless the trail is very smooth. The problem isn't so much with the tread- if the trails are dry and packed, road tread is fine- it's the stability that can be an issue. Road shoes are great when you're running on a flat surface, but when you get to spots where there is any unevenness, you really can feel the side to side roll. The Instinct though is different- it's quite low and flat, and has very little side to side roll at all. As long as the trail is not slippery, that shoe is really great on trails.
For an all around, all year "door to trail" shoe though I really do think you need something with a bit more of a trail specific tread, though the one drawback with that is that trail shoes tend to use softer rubber for better grip, which wears down faster than the road specific soles on road running shoes. Over the past 2 years I've found a couple of really great shoes for bridging the gap between road and trail- the Brooks Pure Grit, the Inov8 F-Lite 230, and most recently, the Altra Lone Peak.
As with anything, when you're trying to find the best of both worlds, there are going to be trade offs, and the three shoes I'm going to write about each have their own strengths, and also their drawbacks when it comes to being an all around door to trail shoe.
First off, the Inov8 F-Lite 230.
This is a great shoe. It's very low to the ground with minimal padding underfoot, and not a super aggressive tread but definitely more than a standard road shoe.
Next is the Brooks Pure Grit. This shoe is great- super comfortable and fast feeling, pretty good grip on muddy trails, but the softer rubber wears down somewhat quickly if you use it on the road a lot.
The third one is the Altra Lone Peak 1.5. I've just started using this shoe, but it feels great and seems very promising. Out of the 3 shoes I'm reviewing today, this one seems to be the most trail specific- it has the most aggressive tread, and a fairly firm ride. I don't think I'd want to wear these for a road marathon like I could with the Brooks Pure Grit, but for a few km back and forth to the trails I think they'll do just fine, and once I get on the trails, they'll be great. My only concern is how well the aggressive tread will hold up on the pavement. I know though that these were designed to be trail shoes and that's where they will excel, and I have a feeling that I'll be reaching for these more often than not when I'm headed out for a trail run
No shoe is ever going to be all things to all people, and that's fine. When I need to do a track workout, I'm not going to reach for my Lone Peaks. When I need to do a steep, muddy trail race, I'm not going to reach for my Brooks Pure Connects- that's why shoe companies make different shoes for specific needs. For those days though when I know I'm going to be covering both road and trails, it's nice to have the option of a shoe that will work well for either, and I think these three are great examples of that. I'm sure that there are many other shoes out there that fit this same description, and it's worth finding something that works for you, and that you're comfortable reaching for before heading out on a run where you don't know where your feet may take you.