Alot of times i think i can run gearlists without my R1, but I rarely do
1. Moving insulation in the morning is VITAL for me. I get out of my sleeping bag, cook, brush teeth, and pack, woah now im a little chilled. I've used a micropuff for this and i overheat quicker than the R1.
2. Don't underestimate the feel of fleece, puffys are warm, but skin on nylon is pretty lame, and I feel it leaves a lot of air as well as a bellows effect for me, channeling my joules away. R1 is nice and tight and cozy and can be worn without a base, try that with your Mica, windshell, or parka.
3. Between the thumbholes, hood and huuuge zipper you get incredible venting and you can button up like your wearing gloves and a balaclava. This is my pick for multipitch climbing below T shirt weather, and for ski touring, and any other time i feel I have the potential to get chilled. I can't explain the magic, but it definatly is also harder to get a real bad flash evaporative cooling moment compared to my midweight smartwool top, when i freeze after i stop.
I'd buy the R1 any day, and I'll probably get one again when i get tired of the piles in mine. I wear it almost every day I can for good reasons.