Installing a motherboard is easy in the Corsair 750D. The cable cutouts are well-placed and the now-standard rear cutaway makes it easy to change out a CPU cooler that bolts to the back of the motherboard, even if the motherboard is already mounted. The case uses raised mounting buttons instead of screwed-in standoffs, and there's a stud, rather than a standoff, in the center of the case, which helps hold the motherboard steady for easier mounting. The tool-less drive bays themselves are flexible without feeling flimsy and they lock solidly into place once snapped around a drive.
The 750D also includes four 2.5" drive bays behind the chassis, for installing SSDs. This is fairly useful if you need to keep the front of the case clear (and you may) and four drive bays is enough for even the most ardent SSD RAID enthusiast. Realistically, it's probably overkill -- you'd likely see better performance from buying into PCI-Express-based storage rather than RAIDing four SATA 6G SSDs into a single array. Alternately, if you have a 2.5" drive from a laptop banging around, this gives you a handy way to install it without reaching for a converter kit.
As configured, the Corsair 750D is a positive pressure case, with two intake fans in front and a single exhaust fan in the rear. If you configure it as suggested by Corsair's Reviewer's Guide, however, it's going to turn into a negative pressure design. The difference between the two is captured by this diagram from Silverstone:
A positive pressure case is a case where the internal air pressure inside the chassis is higher than outside, thus helping to prevent dust buildup. A negative pressure case is a chassis where air pressure is higher outside the case than inside, which typically adds to dust formation as air is pulled through the myriad tiny gaps in any chassis. This is unavoidable. Which kind of configuration cools better depends partly on your components, but negative pressure cases require more dusting than positive pressure and are sometimes seen as less desirable for this reason.