The opposite end of the spectrum held my interest. 2011 into early 2012 was my year of mini-ITX. When my PC building business was still active, I was searching for ways to differentiate and settled on compact powerhouse systems. Research narrowed it down to Silverstone's Sugo Series and Lian-Li's PC-Q08. The latter's available red-anodized brushed aluminum construction really won me over. It's a sexy case:
I knew going in that such a small enclosure posed challenges. Without custom wiring for the PSU and other cables, there's a lot of excess wire bunched inside the chassis, but cable management options are slim. After a few hours of experimentation, this is the best I came up with:
Hidden under there was ZOTAC's Z68ITX-A-E, at the time the best motherboard available. With the advent of Z77, other board companies have started to move into the space, but performance isn't the issue - thermals are. Even with an upgrade to Noctua's brand-new NHL-12 low-profile HSF, an i5-2500K at stock speed crests over 70C. Many people push those chips to the 90C mark or higher but it's not a result I was happy with.
Worse, note the position of the graphics card in the picture. ITX cases have to put their cards at either the very bottom or right next to the side wall and the lack of great ventilation requires spooling the card's fan to 80% or more. Especially in the case of my card, 80% is loud, and the orientation meant all the sound was reflected off of my desk surface into my ears. I play my games with over-ear headphones and even then constant whine of the card grated quickly.
Noise and thermal performance was an issue but the worst problem was myself. I love tinkering with my computer. Swapping a part here, upgrading this, changing that. Changing parts in this case requires a lot of work. I enjoy building computers but two hours of teardown and rebuild just to change a CPU is enough to kill that.
My advice? Stay away from ITX, particularly if you swap a part at least every six months.
Still interested in the form factor? Bitfenix just introduced a case that looks incredibly promising and has gotten favorable reviews. Called the Prodigy, it's slightly larger than the PC-QO8, but it looks much easier to work with for the initial build and any component changes thereafter. It's not perfect but I would describe it as the ITX case with the least compromises.