I recently started hunting for an MPU-401 card for my (finally finished!) DOS retro build, and found that they were so difficult to obtain that some people have started making new clones available. The one that really caught my attention, though, was the one done by lo-tech (unfortunately currently out of stock). They basically just sell the PCB, with instructions regarding which components need to be purchased and soldered on.

As a hobbyist, this really appeals to me. The ability to just build the part I want, instead of having to hunt down a rare part that gets ever more rare with every passing day? Not having to worry overmuch if the thing fails because I can just fix it (easy, since I have the schematics and built it in the first place) or build a new one? Awesome.

I have just two questions that really come to mind about it:
How reliable are the designs for clone boards like these?
And are there other parts sold in this manner that would be useful for a retro PC gaming hobbyist?