About
This is my fifth and, as of writing this (2019-01-12), current personal computer. Bought in parts, assembled and running since without incident (not counting certain Windows 10-related driver frustrations).
It was by far the most expensive one I'd ever bought at the time, and also the one I've sunk the most additional money into over time through peripheral upgrades and additions.

Reflections
Nearly four years in, I am overall incredibly happy with the research and decisions I made (much credit to PCPartPicker for easy compatibility checking!) and how this build has served me.

The CPU has been great for gaming and music production alike. Overclocking was a joy and temperatures have never been a worry with the Noctua beast of an air cooler on it.
The GPU was expensive, but complements the CPU brilliantly. Couldn't have asked for much better (the Ti model was not out yet) and it endured my bitcoin mining curiosity for a couple of months too.
Beyond impressed with the case which certainly set a new standard for me personally; almost can't believe the low price in hindsight. Quality construction, plenty of space, easy to work with, good options, great dust filters and just amazing noise dampening.

I have much to learn about RAM still, and no idea how the 1866MHz DDR3 CL10 sticks match the rest of the build in performance. Options were limited having to fit under the giant Noctua cooler and taking into consideration what was easily available and, ultimately, cost.

Was surprised to still encounter the occasional need for DVD, CD and even Floppy drives, but at this point I think the external devices I ended up getting suit me best anyway.

Honestly - not a single real regret. Now there are certainly some features I will look for in my next build which this lacks (or had to have tacked on, like USB 3.1/C), but for 2015, the knowledge I had and the price I was willing and able to pay - this has been a 10/10 machine.

Additional hardware / notes - not (yet) in builds.gg system
USB Type-C Connector: ASUS USB 3.1 Type-C (PCIe-x4)
Monitor 4: SWEDX SM28K1-01 4K 28" 60Hz
External HDD: Intenso Memory Center 4TB USB 3.0
Docking Station: ICY BOX IB-120StU3-Wh (for a handful of old HDDs)
External DVD Burner: ASUS ZenDrive U7M (SDRW-08U7M-U)
External 3.5" Floppy Drive: Hama Floppy Drive External USB
Audio Interface: M-Audio M-Track 2x2 [USB-C]
Headphones: Beyerdynamic DT 880
Speakers: Edifier Studio R2000DB
Microphone(s): Antlion Audio ModMic 5 (Røde NT1-A, Røde Podcaster USB, Behringer XM8500)
Headset: Plantronics RIG 800HD PC Dolby ATMOS
Mousepad: Razer Goliathus Speed Edition
Mouse Cord Management: Mouse Bungee v2 Silver
Connection: 250 Mbit/s up & down