Congratulations on recognizing that the 5 inch "never dull" won't cut it. Now, if I can just get one of my sisters-in-law to do the same (I suspect she was the one who brought the "Miracle Blade" to the joint family vacation house and left it there), life for me would be simpler.
I'm also not seeing very much feedback on the Masahiro. However, I am seeing where Chef Knives To Go is offering presumably the same knife on their web site for $136.50 for the 10 inch size (same steel, same 20-80 edge profile), or 32% less than Williams Sonoma. No user feedback either site.
But mebbe we need to put the cart before the horse here. Yes, you need more than your proverbial "never needs sharpening knife" But even with a more conventionally edge knife, you will find that with use comes the inevitable dulling of the edge, So you need to both slow the dulling and to (eventually) reverse it by getting your knife sharpened. Slowing the dulling process means having a proper cutting surface and having a means of honing the edge. Getting your knife sharpened means just that.
Your knife skills class probably had you at least using some sort of cutting surface. The best in terms of minimizing damage to your knife's edge are end grain hardwood boards. Edge grain hardwood boards will be a bit harder on the edges, and will be harder to maintain, as well as more likely to develop grooves which can harbor pathogens. Bamboo boards are harder on edges than wood boards. Plastic boards a lower on the desirable chain than bamboo. Composite boards are basically wood fibers in a glue matrix - almost the worst. But the absolute worst are marble, granite and glass.
You're going to want a good honing rod. I will shill one immediately - the 12 inch Idahone. CKTG carries it for $30.
In your knife skills course, did you review or (better yet) practice sharpening? If so, then keep it up - by buying a good quality general grit (800 to 1200 grit) stone of decent size (at least 2" x 8").
For a quick sharpening review, I would suggest this:
I would also suggest you look at videos by Jon Broida, Murray Carter and at Chef Knives to Go.
Sharpening with a stone takes practice. But it's not all that difficult.
If you want to minimize the learning curve, you might want something like the Edge Pro Apex. Chef Knives to Go offers a custom kit the "Essentials" with Shapton Glass stones for about $230. I have it, use it and can recommend it without qualms (except for price - but that can't really be gotten around).
In short, a good cutting board, the Idahone and a way to sharpen your knives will have more of a positive impact on your food prep than just getting a new knife.
Now, as to Williams Sonoma - and by inference, all retailers. You have store credit. My IMMEDIATE advice is to check to see what your options are concerning how that credit exists. Is there a time factor? Some credit policies require you to "spend it or lose it". There might be an "evaporation" policy, where you get charged if you do not use your account - or you might be charged monthly anyway. Can you cash it out? Does your state have laws which restrict retailers on how they can deal with such situations? In short, you need to know what your options are. For what it's worth, I have no idea about what Williams Sonoma's policies are - but if it were me, I would start digging into the fine print asap, no matter what.
At this point, it's almost 2 a.m. for me, so I'm calling it a night.
Hope that helps.