I have 3 Red Sex Links and 4 RIR's. The two breeds are very similar, and nearly everything I write here about the RIR's applies to the RSL's except that the RSL's lay bigger eggs.
First, let me say that each bird has its own personality. Overall, the RIR's have very good personalities, and I think that has a lot to do with how I have treated them since they were little (just feathered out). My neighbor's birds -- including his RSL's and RIR's -- are all terrified of humans and basically feral/crazy.
None of my birds have had health issues that couldn't be corrected with yogurt. I feed them "layer" feed, scratch, oyster shells (just a little...the feed already has calcium), and some dried meal worms. Most eggs from my RIR's weigh about 60g -- "extra large" at the grocery store. One RIR was the first of my flock to start laying, at 17 weeks, but all were laying by 6 months.
They love to forage and eat grasshoppers, stink bugs, millipedes, crickets, worms, creepy-crawlies, mouse/vole corpses, grass, leaves, seeds...you name it. They enjoy free ranging -- they are curious and like to forage all over the property, but they also like getting back in their "home" and really chowing down on feed and then rehydrating before hittin' the hay. I generally free range them for 2-4 hours in the evening and make sure they're back inside before sunset.
Like most/all chickens, they are naturally fearful, though they'll peck at my leg if I loiter in their run without feeding them...kind of like, "Hey! Hey you!" They did that with the electrician who was wiring the place, too.
Their "inner coop" (where they sleep), their food, and their nesting boxes are all about 30 inches off the ground, and they have no problems flying up to them even though they are pretty chunky birds.
They are very cold-tolerant, though they don't like snow and will go pretty far out of their way to avoid walking through it. So it's not like they like snow and cold, but they can handle some pretty cold temperatures. Admittedly, they sleep in a coop that has a heater that kicks on at 32 degrees and turns off at around 48 degrees, but they've been outside on days that never got up to 32 degrees and did fine.
They REALLY don't like heat! So even though they LOVE chasing down grasshoppers -- I think they like the thrill of the hunt as much as the taste of their prey -- they'll sit in the shade all day rather than deal with direct sunlight. I would not get these birds if I lived in a desert-ish climate -- that would just be cruel.