I have the 240mm Ikazuchi and it's been an amazing knife so far; some cucumbers have had their way with the core steel, and there it now sports a mild patina. For the handle and saya, I've used the JKI saya and handle wax. It's been wonderful for this and all of my other knives, and adds a noticeably darker, richer color--which I really appreciate--in addition to whatever its protective qualities may be. So a huge thumbs up (albeit from a novice!) on both the knife and the wax.
I've had mine for a few months now. It's my first j knife and like it. Tomatoes seem to be a minor challenge but the performance there is directly related to my sharpening.