For the conditions you describe, boots may be more appropriate than trail runners, especially if there's a need to kick steps in the snow.

Remember, you did 18 miles, which is a long hike, especially if you aren't used to walking that far, and if much uphill/downhill is involved.

Irritation on the top of your toes might mean that the boot doesn't have enough vertical room, or maybe that the insole is too thick. Also, if the irritation happened on the downhill leg of your hike, the boot could be a bit short, causing your toes to hit the front of the boot. Another thing to check is the possibility that the forefoot of the boot is a little narrow, pushing your toes together. You should be able to wiggle your toes inside the boots.

Irritation of the arch is less common...do you have a rather low arch? Many insoles (maybe most) have a pretty sizeable "support" under the arch.

I'd have to disagree with OregonMouse about the need for a break-in period. It's true that they should fit right from the start, but traditional, stiff, all-leather boots do require breaking in. I'm talking about top grain outers, leather lining, leather insole (not too common now), and leather and rubber midsoles, and Vibram outsole. Salomon makes lots of different boots, so not sure if your are similar.

I gather that most everyone on this board has moved to either light, flexible boots that don't require breaking in, or trail runners. Me too.

I have the Keen Targhees. Not sure what the difference is in the Targhee III. They've been comfortable and durable, and I like the wide forefoot. Too flexible for kicking steps, most of the time, for me at least.