The Corsair Carbide 300R is certainly an interesting chassis. While its bigger brethren like the 400R or 500R offer a bit more value for your money, it becomes quite apparent that the 300R lacks the firepower in terms of features to really take on the likes of the Midgard II for example. Not having USB 2.0 support or more drive bays to hold 2.5 or 3.5" units puts a real dampener on things. On top of that, it lacks the small things like grommets for the water cooling tubing or motherboard tray. While it offers very good quality in terms of how the materials are used - especially when comparing it to the Midgard II or BitFenix Shinobi, this may not warrant the high price, as the customer in this market segment is driven by features, not so much by build build quality.
So, if a very solid chassis is your cup of tea and price is not really important you will not be dissapointed by the Corsair Carbide 300R, otherwise you should really think long and hard, if any of the many other cases in the market may be more up your alley.