I've always been satisfied with their RAM, never tried their SSDs. I once got a new Corsair PSU that was completely dead right out of the box (TX650)... but I quickly got a replacement (TX650 V2) without much of a fuss and I haven't had any problems with said replacement for five or so years now, so no hard feelings.
I am the bringer of death. Fall to your knees and beg for mercy... Or give me a sandwich, I'm pretty hungry.
Corsair is generally solid across most of their product line, but they are certainly not the be-all-end-all manufacturer.
Their cases tend to be very good, especially in terms of cost to feature ratio, and they do tend to pioneer new features and set new standards in the case market, such as making rubber grommets and all black interiors and cabling pretty standard. They definitely have some strong competition though, and I would rate manufacturers like Silverstone and Lian Li a little bit higher than Corsair, generally.
For PSUs, Corsair is definitely a solid brand. Most of their high end units are manufactured by Seasonic, and their AX series is nearly identical to Seasonic's X series. Not all of their units are from Seasonic though, so definitely do your research before buying. I bought an AX860 and it's been pretty good so far, mind you I haven't had it that long.
Memory is memory as far as I'm concerned. I usually just buy what ever is a good price that doesn't look like complete ass. Getting Dominator RAM is a waste of money IMO. They do seem to have the widest range of colours for their RAM, especially for low profile RAM, so there's that if you want colour coordination. I went with some low profile Vengeance RAM myself.
Their SSDs I have no experience with. I haven't heard bad things, but I think Samsung is currently top dog for SSDs.
For peripherals, I have a K90, and it's pretty great. I love that it's aluminum, it seems very rugged. It could probably be used as a murder weapon. I haven't used their Mice, but I've heard alright things. The sensors are supposedly a little flawed, but not unbearably so. And, once again, aluminum. No experience with the headsets, but 'gaming' headsets in general are second rate, the only one that can really stack up to decent headphones that I know of being the Sennheiser PC360. They're probably not bad compared to other gaming headsets though.