I've used the one listed in the opening post (well, the double-entry version, but same size and from the same site) for my TMNT cabinet. I've been happy with it. The cabinet is small, so a full-sized over-under coin door wouldn't fit. I went with the one from X-Arcade because of the dimensions listed on the site, so I was able to measure and make sure it would fit (hard to tell the exact measurements on some random coin door on eBay). Though if you're building a larger cabinet, then any used coin door on eBay would work nice.
On my "full-sized" cabinet, I do have a regular over-under coin door.
Both cabinets have working coin mechs, and take quarters.
I keep a small bowl of quarters nearby to play. It still feels better to me to insert a quarter than using just a button to coin up, or using a shifted-button combination on a MAME machine.
A coin door is also a great place to put admin controls and other stuff (like USB and ethernet ports) out of the way.