Its best feature is the light weight, but the trade off is durability. I have three raid packs from salomon, 10L, 20L and 30L. Generally I'm happy with them, and I've had the 20L version for about 5 years, but all three have had non-critical breakages, like the stitching around mesh pockets falling apart.The other thing to note about the 30L pack is that it is quite a large pack to have very little support in the back panel.
Let me know if you have any specific questions, let me know and I'll do my best to answer them.
One more vote for: Officially - NO; unofficially - yes (occasionally).
If you want to have a go, just to see how you get on with winter walking, then you might as well try it with your existing boots. Make sure that you get some with flexible bars though. Grivel sell flexible bars separately.Also bear in mind that your feet might get a bit cold in boots without insulation, and that some crampons could damage the front of the boot if you try anything too steep.
I know people who have been put off winter walking because they were advised to hire full-on, rigid, C3 compatible, plastic boots for their first foray into the snow capped Cairgorms. Blisters were the main result. Others got by with summer boots and had a much better time.