The location of the PSU and the compact size of the interior will require you to install the power supply first before adding any of the 3.5" hard drives. Doing so is quite easy for both. You do need a screwdriver to secure the PSU, but the hard drives will utilize the plastic brackets. While this does stop the drive from sliding out, the plastic contraption still allows for a lot of play and can pop off quite easily—definitely not something you want to occur while transporting the system to the next LAN party.
Installing the motherboard is easily done, but things are quite tight. You need to angle the board a bit to get it into place before using screws to secure it onto the standard motherboard spacers. Certain conditions might block the internal 3.5" hard drive bays if you use a large top-down cooler. You would probably be better off using a smaller tower cooler instead.
Installing the storage drive to the floor of the case is quite easy. Simply place it there and secure it with four screws. You may pick the direction the connectors face.
To install the optical bay, you need to pop out the drive bay cover first. Once free, simply slide it in and push the larger plastic locks into place. Just like with the 3.5" variants, these do not hold well, so you better use screws to prevent the drives from vibrating or moving around.
With everything in place and some time invested into hiding cables wherever possible, the chassis is quite full already. You should, however, easily be able to install a multi-GPU based gaming rig with a H80 or 120 mm tower cooler into the case.
With everything turned on, the Cougar Spike makes a simple impression. If they would have included an LED-equipped fan in the front, things would have turned out much cooler. Due to the compact size, the large top-blow cooler comes pretty close to the side panel, which means that you need to watch the height of things if you plan on installing any fans there. Taking a quick look at the rear, there is nothing out of the ordinary as everything is easily accessible.