In addition to the click, the key then requires less force to bottom out providing positive tactile reinforcement the key hit home.
The biggest issue on rubber keys is not punding them hard enough so I have missing letters on a regular basis. For example the line I just typed. I am not going to edit it for the missing letter as I am typing on my laptop. The remainder of the red lines I did correct so one error is not a typical keyboard induced typo. In reality it is much more. Re-typing requires extra time, mental process, and distracts from work, so a good keyboard does improve productivity and accuracy.
My Keyboard of choice is the IBM Model M hands down. For ergonomics, the tactile feedback is perfect with less proofreading required. The dish shape over a flat keyboard is a huge ergo win and preferred above split keyboards. Did I mention I hate flat keyboards? The key caps are dished and reduced in size so centering your fingers on the keys is natural, unlike square flat keys created by some artsy creative designer. Laptops often favor the square keys as there is less room for dirt and crumbs to fall between the keys. Unfortunately, for a touch typist, getting off center and pressing double keys is a common problem.
Look for a keyboard that you can feel it has made the stroke by feel and the screen really shows the output. Some rubber keyboards do buckle and appear to have bottomed, but still fail to register a key press. Look for one with dimples in the keys so the fingers naturally settle into the centers. and last find one that is NOT FLAT, but curved so you don't have to reach for numbers etc.
Avoid keyboards with extra keys resulting in a small return key. Hitting extra keys that are where you normally have the return key is bad. Having an extra long reach to hit is is an ergonomic issue.
Did I plug the IBM Model M? One without the Windows key is Ideal if you can find one.