lol I just realized... Technically it does support slim WC rads: they didn't say that you could have fans too
Based on what little time I've had with the case:
They took the HDD cage from Arc series and made it 100% removable and 5+3 instead of 4+4 drives. They also made the case wider to accommodate 140mm fans all around. However the top fans aren't offset like on Arc series which is good from aesthetics point of view but essentially makes the top incompatible with watercooling.
Now that the case is wider, there's a lot more room on the back side of the case for cable routing (slightly under 20mm with the foam on the sidepanel included): that's very good since the R3 is a bit limited on space behind the mobo tray. The SSD mounts on the backside is a good idea but mounting is awkward since the screw holes will be behind your mobo. You can also, if my workmate isn't a retard, fit the huge Phanteks in the R4 He did say it was tight though.
Some people may love the integrated fan controller. Personally I don't like it but it's fantastic on pre-built systems.
Overall the case left me with a bit confused thoughts: it is clearly an upgrade, and it fixes some of the annoying little things on their cases like the fixed (lower part on arcs) HDD cage. However since they made it a tad taller than the R3, they could have made it even a tiny bit more so that you could install a watercooling radiator with fans
on the top of the case without worrying too much about your mobo or RAM interfering.
As a successor to the R3, it's a winner. It just could have been so much better. Overall, I'd say it's 8.9/10.Sorry for all the typos, I'm not going to start to hunt 'em on this rather long post.Edited by Blizlake - 7/20/12 at 5:16am