It's my favorite form factor. Graphics will always be handled externally.Mini-STX is just a weird concept to me. The only thing I can think if is how Intel loves to overrate their onboard graphics. Sadly they are still not up to snuff for anything but light gaming. STX boards would do well for HTPC use, but the NUCs already have that under control.
Micro-STX is an improvement, but the dearth of decent MXM boards will hurt it. Still, I think the ability to use a unified heatsink for both CPU and GPU will help things greatly on the small-small end. That has been the catch with ITX for a while now, the GPU always ends up facing away from the CPU and thus two discrete heatsinks and fans are normally used.