Yeah, I tend to favor the CAK over other models, myself.
If it's a polished one, they don't rust too easily, but they will rust. They will also patina (a dense form of corrosion that gets to a certain point and stops, and prevents further rust -- same process as "browning" done on old muskets and such). This will happen naturally, or it can be induced. Or just keep the blade clean and oiled.
I store mine in their sheaths, and live near the Atlantic ocean. No rust. Just keep them clean and oiled (I like to use mineral oil), or wipe them with a silicone gun & reel cloth, and you'll be fine.
As for how usable and how strong? The AK is the strongest of the HI kukris, and the Chiruwa AK (CAK) -- the one with the full width tang pinned in place, is the only one they warranty as a prybar. It's an absolute beast of a blade. Some find it too heavy, I find if you wear it baldric-style it's not a problem. As for usability, it's the mother of all choppers. You can put a convex edge on it that will last a long time, or do a straight zero-edge on the final bevel, and it will cut light vegetation with a flick of the wrist and still chop like crazy, at the expense of having to sharpen it more often.
In summary, it's the toughest blade HI makes, and I'd put mine up against any other chopper out there. Even had a custom rig made for it.