Montane promote the Lite-Speed jacket as a windproof on their website. I've worn this jacket a few times in slightly adverse conditions, and I think windproof sells it short. Here's why!
The Montane Lite-Speed is made from Pertex Microlight, a material that was created in 1987 in conjunction with several leading outdoor apparel manufacturers. Microlight is extremely light, nearly as light as Pertex Quantum.
The jacket is of quite a generous cut but is extremely light. So light and compact that it fits inside a tiny stuff sack that fits easily in your hand. Not as compact as the Rab Cirrus, but it's comparable. It also weighs around 50% more than the similar Rab Cirrus jacket.
The Microlight material is a micro-rip-stop type which feels quite robust, although I say this within reason, i.e. within the realms of lightweight materials.
Unlike the Rab jacket, it has better adjustment for the hood, with cords that can be altered to open or close the opening enabling you to close the hood right down around your face.
The jacket's material feels quite soft although it does have a slight bin bag feel. However, it doesn't feel clammy, but it is not as soft as Pertex Quantum. The wrists are elasticated and have a nice level of tension meaning while they hug your wrists, they don't squeeze them. There is a full length zip that works nicely and it includes a storm flap behind it which sort of suggests more for this jacket.
There is also a hem drawcord to allow you to close down the hatches further and keep the elements out.
And the jacket packs down pretty small, about the size of a small grapefruit.
I've been using the Lite-Speed jacket during the summer months in general, times where it looked like rain was possible, but not likely. And to be honest it didn't see any use. But recently I've used it a couple of times in the Peak District and it has done well.
I recently went up to the Derwent Edge where the Met-office had forecast a very low chance of rain......yeah right. They made a hash of that one. While heading towards Lost Lad the rain started to come down quite heavy, not a downpour, but enough to soak you through without any waterproofs. I put the Lite-Speed on and continued on my way. Temperature wise it was fairly warm, in the low teens, which for me is warm.
I wore the jacket for a couple of hours and can safely say it did not make me perspire unlike some waterproofs might have. It was comparable to the Rab Cirrus and it's Pertex Quantum, a little warmer than the Rab. But the surprise was how waterproof it was. It kept out a fairly heavy 15 minute Peak District shower without a sign of it wetting out.
The Montane Lite-Speed, to me, falls between something like a Rab Cirrus and a full blown, lightweight, waterproof jacket. If you walk warm like I do it will probably be better used as a winter windproof, with the Rab Cirrus used in the summer. It also has a use as an extremely lightweight waterproof if you really want to get the weight down and are only expecting lighter rain. It can also be bought very cheaply if you shop around.