I had a half a dozen redcaps around 5 years ago, from McMurrays. Since I had to get 25 chicks, I ordered a bunch of other breeds and decided to try the redcaps because they were unusual.
They are a nice breed. The combs are just wacky, more so on the roos. One thing I observed about redcaps is that they are a bit flighty and panic easily, so if you don't like startled chickens squawking and flapping when you have to round them up for their annual blood test, etc., then you might find them a challenge to work with. They also will not set so you have to incubate redcap eggs.
Other than that they are quite nice. They're a medium-to-smallish bird, the eggs are off-white and not very big. Because they are rare, it would be good if more people got intrigued and wanted to try them. I eventually sold mine because I was working with Nankins - another rare breed - and didn't think it was right to keep the redcaps when I couldn't give them more specialized attention.