The Roclite 319 is one the newer creations from UK manufacturer Inov8 replacing the discontinued 305 and 320 models. I've put about 100 miles on my 319s and my first impression is very favorable. Inov8 markets this shoe as a great choice for road runners switching to trail running for the first time who are used to overly cushioned trainers. I think it's also good for experienced trail runners looking for a long distance training shoe. Here's my take on the 319s from the ground up.
Outersole: The sole design is the same as other Roclite models with deep lugs that provide good traction on a wide variety of surfaces and good gripping power on muddy trails. The hard endurance rubber will last for several hundred miles but the trade off is less traction on wet rocks and roots when compared to Inov8's sticky rubber sole utilized on some of it's other shoes.
Midsole: The single density sole is rated 4 arrows which means it is the most cushioned shoe in Inov8' stable (They use a one to four arrow scale to measure cushioning). The single density sole (305s had single density midsoles) is softer than the dual density sole of my 320s but still protects the foot from hard, sharp objects. It may break down sooner than a duel density sole but I don't have enough miles on them at this time to make that call.
Uppers: The uppers are more roomy than the 320s with a higher, wider toe box that is much appreciated by this runner. There is a heavy duty rubber-like material that wraps around the shoe. This helps make the shoe very supportive but also prevents water from draining quickly. This can become an issue on long training runs/races with many water crossings. I really like the design of the thin laces. One pull is all you need to tighten up the shoe and the laces stay tied. Not something I can say about the laces on my Cascadias.
The 319s are a best suited for long-distance training or racing on techincal trails. They are not suited for short, fast runs due to their weight and structure. I like to wear my 295s for the short stuff! Overall, another great shoe from Inov8.