Our 9.9 kicker has saved us from disaster on a rocky lee shore at least twice - when kelp had blocked the water intakes and caused the main to overheat. Also brought us back 12 miles or so twice after engine or sterndrive problems, once from part way up into Glacier Bay. And once when steering let go right in the crowded Hartley Bay harbor, with other boats only yards away.
We could have been saved by a tow in only two of these situations. After 40,000 nm cruising, I've had enough such adventures to really love my kicker. Oh, and it's great for salmon trolling.
i do make sure my kicker is running well at the beginning and end of every summer cruise, and I use it frequently through the summer. Basic maintenance is simple but important. Every time we really needed it in a hurry our kicker started right away.
First one was a Suzuki 9.9 2-stroke, and our current one is a Yamaha 9.9 hi-thrust 4-sroke. The Suz moved our CD 22 at 6 knots, and handled the ups and down in the giant waves I mentioned in the other thread. The Yam moves our heavy 26-footer only 4 knots, so we can't always make it against the currents up north. But we can get over to the side and get out of the stronger flow, or stay safe until current lessens. Did that in Glacier Bay.
I just replaced my raise/lower type kicker bracket, worn out after 10+ years (and many miles bouncing along the roads), with a newer and much beefier one. It's WM's sturdiest, rated for up to 170 lb. List $400. Vertical travel 15.5" IIRC. It seems to be much the same as Garelick's sturdiest.