I've used a few different adapters, but when it comes to adapting an F mount lens to a Canon EOS camera this is the best product I've used. There's still plenty of room for improvement, but it's a pretty good situation.
* Snug fit - it may feel difficult to attach and remove from the lens, but this is how the adapter makes a firm, solid connection.
* Dual iris tabs - there are two blue tabs for changing the iris/aperture opening. They fall on the bottom left and bottom right of the camera when mounted - right where you need them.
* Robust build - for what it is, the build quality is fantastic. Please bear in mind these are very small metal components. The ring won't fall apart, but if it's loose in your camera bag it won't survive.
* Price - yes, it's finely machined metal, but it's still a small hunk of metal with minimal electronics. $100 is a lot to spend for what you're getting.
* Electronic connection - the ring can be programmed to report EXiF data for a focal length, but it involves shooting several frames off in A mode at varying aperture settings on the camera. It's a mess. You can roll the aperture dial and tell the camera I'm at f/4 and it'll record that. To be clear, there's no communication between the lens and the adapter. These aren't limitations from Fotodiox, but from Canon or from the nature of adapting F to EOS.
* While shooting video the iris tabs are sufficient to do an iris change if it's absolutely necessary, but Nikon lenses aren't designed with this in mind, so don't expect a smooth ramp.
At the end of the day it's the best product I've come by, and while I don't regret owning it one bit, I think the price is a bit steep.