While the B2 is not exactly a small enclosure, it is tight enough that a removable motherboard tray would be really nice. Consider where the headers are located that attach to the front panel controls, internal speaker and power button and you will note that folks with gorilla hands will have a challenge. Not a deal breaker, but it would have been a nice thought to include this.
The installed board shown above is a full sized ATX variety and it fit with no issues. While the room between the SATA ports and the hard drive cage isn't really plentiful, there is enough space to allow you to get all of your cables installed with little issue. There are little cubby holes located beneath the hard drive bays and beside the FDD bays, so you can still handle the cable management aspect of your installation.
The initial build used for the B2 consisted of a X1900XTX video board, which is a rather large board. No issues were noted with regards to either the length or height of the board when the fans are positioned in their default orientations. Try to rotate the side fan 90 degrees, however, resulted in a problem.
Namely, it didn't fit. This is the issue I mentioned earlier and will affect all who have a long video or sound board. You simply will not be able to make use of the extra cooling for your hard drive cage if you are using a long peripheral.
Retention of your peripheral devices is easily handled with the tool free clips. As shown here, even if you have a board that is higher than the bracket, the clip will sit to the side of the PCB allowing it to be firmly mounted.
As noted earlier, most of the drives you will install will make use of a rail system. Each rail is made from a combination of plastic and rubber. The primary rigid portion of the rail is plastic and this is where the two metal pins and metal securing tabs are mounted. On each side of this rigid rail is a piece of rubber, one that sits against the drive and the other that sits against the metal cage that the drive will be installed into. This will effectively dampen the vibration and noise that could be produced when installing a metal drive into a metal cage.
To use the rail system, simply place the rail against the side of the device and make sure the pins are seated in the mounting holes. From there you need only slide the drive into its appropriate drive bay until it clicks into place. From here, the drive will not move and will not make a bunch of noise, even when it spins up.
Above is a hard drive that has been installed into the bottom drive cage. Hard drives will be installed internally while optical and floppy drives will be installed from the front. This means you will need to remove the front bezel to install them, but this is not a big task and is easily accomplished.