I use my savekey all the time. There are a decent amount of homebrews that use it, but I have a few favorites I keep going back to. Having the savekey is what probably kept me interested in some of the games. I like being able to go back and try to beat my high score. I love the look of the savekey too. I feel like it's something Tom Baker would have pulled out of his pocket on Doctor Who.
Tom Baker's voice,
"Have a Jelly Baby.. Oh, wait, that's my savekey."
I did one small modification to mine. I found with the bright blue LED, I would often be looking at the savekey, instead of the TV. I took a small 1x1 mm square of aluminum tape and placed it on clear plastic, directly over the LED. Now the entire thing has a nice blue glow, but it's not as distracting. I also have a padded case I repurposed for my Harmony Cart and I cut out a bit of the foam to make a little compartment for my savekey. Now both items are kept safe when I'm not using them.