My first (and presently only) hand-made Japanese cooking knife, purchased just over a month ago, is a Moritaka — the 210mm Aogami #2 gyuto. I'm still relatively new to the hand-made kitchen knife world (have only been studying it for a few months), but I can say that this blade just sings for me. It is incredibly well-balanced (for my taste in knives, anyway), very light, but still feels substantial enough to demand respect. I really love the rosewood handle, and the fact that the carbon blade is forged to a stainless tang (to prevent damage, corrosion, etc from the inside-out). And, most importantly: it takes a wicked sharp edge, and holds it very, very well.
By “lacquer,” I'm guessing you're referring to the kurouchi finish on the blade. This won't prevent a patina from forming (especially on the cutting edge of the blade, where the kurouchi is polished off), but it will slow the corrosive process that leads to rusting of the blade — again, just where the kurouchi hasn't been polished off. The portion of the blade that is “naked,” that being from the edge of the blade up to where the kurouchi begins, is still just as prone to patinating and rusting, and requires the proper care given to any carbon blade (be prompt about cleaning it and keeping it dry; keep a slightly damp and/or dry towel at hand for longer prep sessions).
A patina is nothing to be concerned about — in fact, some people work hard to achieve a specific patina. The patina will lessen any negative effect the carbon blade might have on your food (discolouration, foul scent) because it slows the reaction of the carbon in your blade to the acids and other reactive agents in the food. For what it's worth, even without a patina, my Moritaka has never discoloured anything I've cut, including onions and acidic fruits; only caught a bad smell once (mango). It has since developed a lovely, misty patina, and I don't bother polishing it off (though some people prefer to do this). Other board members here can explain global preferences for patinas better than I.
Long story short: don't worry about the patina. Practice proper maintenance and care of your carbon blade, and you'll be fine; with time, it will become second nature. It's not really as scary as it might seem (you won't ruin the blade unless you're *really* careless!)
I used a MAC santoku recently, and was very impressed with it (very sharp, nicely balanced), though I still prefer the rustic and unique character of my Moritaka (plus, being a carbon blade, it's quicker to sharpen whenever it might need it).
I've heard wonderful things about Masamato, too, but haven't had the opportunity to try one myself.
(Board members more veteran than I: feel free to correct me if anything I've said is inaccurate!)
Edited by cpeters - 5/14/12 at 2:55pm