I've used my litespeed for almost a year now. It is my favorite wind shell for backpacking, trail running, and backcountry skiing. A couple of comments:
1) I'm afraid that I have to disagree with Ryan about the sidepanels. Montane's website claims the side panels are "PEAQ", not Quantum. Using an informal "blow-thru" test, the fabric seems to have greater air permeability than Quantum, more comparable to Equilibrium. These panels are a great feature of the jacket as they add substantial breathability just where you need it -- sort of like the mesh armpit panels on Marmot's driclime windshirts, but with better weather protection. (Ryan -- I'd welcome your comments about this....)
2) I love the flexibility of the shell. I'd say the extra warmth of the hood justifies its weight, although I think the dual-layer construction is overkill for most conditions where I've used it. (I suppose you could cut the hood liner out and save a few grams if you wanted to.) Also, if you do carry a hooded storm shell or poncho, the litespeed hood can be rolled up into a gasket around your neck to minimize chimney-effect heat loss there.
3) One trick that the full zip and light fabric allow is to fully unzip the shell and pull the hem through the shoulder straps of a pack during periods of high exertion like extended hill climbs. This lets your arms breathe because they are not closed off by the pack straps (a poor man's pit-zip!). You can then instantly zip up and/or don the hood when you get to the top.
4) My size large weighs 5.2oz, which is not the lightest windshirt out there these days. But it remains my favorite due to the hood, side panels, and ventilation options.
5) What I'd really like to see from Montane is a 4 oz Quantum full-zip windshell with a single-layer hood and the PEAQ sidepanels. Oh well, I need something on my gear wish list for next year! ;)