I have happily put together my latest desktop a year ago, returning after many years from abandoning the personal construction route. I figured at the time that it wasn't possible to extract significant price or performance advantages, with the introduction of Intel's Core2 hardware supremacy and box stores relentless commodification of the PC. So my purchased PC machines after that point weres desktops, and then laptops replacing the desktop.
Nowadays, I believe the motivating benefit are the performance advantages in selectively-purchased hardware, like SSDs, multi-terabyte drives, cutting edge graphic cards, and i7/Xeon CPUs. Yeah sure, you can select those features into a pre-ordered box, but it doesn't result in price savings or "optimal" hardware.
As for putting together computers, its "same as it ever was". Its even less ideosyncratic than 8 years ago. But you're still stuck learning the new part connectors, BIOS/UEFI details, hardware trends, etc. Along with the great suggestions like pcper.com, I'll throw in pcpartspicker.com. I recommend it, not so much for the construction articles, but for the database of consumer computer components. It gives you an idea of the prevailing prices of specific parts, and a handy personal page of your parts purchases. You can also then sift through other people's construction sheets and compare your purchases.
Yeah, I envy your plunge into workstations. Its significantly expensive hobby though, much more so than gaming machines.