Just moved my rig in to one of these today. Moved from a CM690-II Advanced.
Case is nicely built. The front door is nice and solid. The power LED on the front panel is white. Haven't had any of the reported problems with the side panels rattling. Push button release for side panels is great. The inserts that cover the optional fan positions are easy to remove - click to release and reseat. Cover for front fan filter works the same. The side and top inserts are not a perfect fit. They're a nice idea, but in a way I'd rather Corsair had left them out as this is supposed to be predominantly a quiet running case.
Plenty of room for components. No problems fitting my 6950 and Megahalems cooler. Runs very quiet with the stock fans, but on the other hand the intake fans are only running at 800rpm with 1200 at the rear exhaust, so not huge on the airflow side of things.
Temps are very similar to the 690 which had two more case fans than the 550D. Definitely quieter than the Coolermaster.
Now a few gripes...
First the door - I don't really like doors but compromised here as it makes the case look great and is so nicely finished. But, it is a pain to open. Because it opens both ways it is held by a pins at the top and bottom of the door on each side which when closed click into clips. This means you really need to pull at the top and bottom of the door to open it, not the middle as the clips hold really tight. Corsair do include a couple of spare pins for the door, and if you open the door a lot you may well need them! You can remove the door completely but that rather defeats the object
The drive caddies work well, but feel really flimsy without a drive fitted.
The case didn't include a 5.25 - 3.5 faceplate, unlike the Coolermaster. So now my 3.5" card reader is homeless for the time being. Thought that was a bit stingy for a £100+ case.
Now the main gripe - space behind the motherboard. I did manage to stash all my cables in the end, but only just. The cable tie loops in the back of the motherboard tray are very tight so you'll need thin cable ties.
The main problem area is around the drive bays. Unless you use right-angle connectors you'll probably find that the side panel will be pressing against your SATA cables. My side panel bows out ever so slightly here, so I may have to get some right angle cables. I think the problem is that the drive caddies have the drive mountings too far back into the bays.
Anyway - sorry to ramble on. Overall this is a great case - really nice looking and well built. If anyone's interested I'll try to get some pics up tomorrow.