I ordered the Red Rum in a small back in January for a trip to Japan in February.
Sizing is wonderful. Slim but roomy enough to get four layers (including a hoodie) underneath. (The hoodie does cause it to be a bit tight around the neck when done all the up though.) After the first day, being over cautious with a hoodie, I found the jacket was warm enough to just be worn with a long sleeve top and t-shirt - even on an open chairlift. Even then, I still had to open the vents on the sunnier days. Temp ranges in Japan were roughly -5 to 1 degree Celsius.
As previously mentioned, Red Rum isn't exactly 'red'. It is definitely more pinkish in real life. I was a little disappointed when it first arrived but got over it. Luckily I wasn't matching it to anything though ;) In photos though, it does look red.
The only complaint would be the stitching of the buttons (which are even more pink in real life), particularly on the cuffs. I ended up losing one on the mountain just all the removing of gloves :( I need to see if it came with a spare button otherwise I'm going to have to try and match somehow... Definitely worth resewing them ALL before heading out for the first time...
Would still totally recommend this jacket to everyone :)