The most important point I would like to make is to try as many different models/makes of pianos as one can before making a purchase decision, assuming one wants a piano with good sound and good touch/action suitable for oneself.
In general, I think Boston pianos are GOOD pianos -- but that does not mean they represent good VALUEs compared to the alternatives (but if the Boston is really what you want and you can afford it, than it is a good value for YOU, doesn't matter what anyone else says). In the US, the Bostons are routinely compared to the Kawai RXs and Yamaha C-series, and both are usually priced at the same level -- but I have recently seen some prices in Asian markets where somehow the Bostons are priced at a significant premium to the Kawai/Yamaha's and the Kawai/Yamaha's seem to be priced lower in Asia than in the US; when I see price descrepencies like these, I have to rethink the dollar valuation of the pianos.
I just don't think one should equate a Boston to a Steinway hoping that just because the same company sold both brands the famous "Steinway special sauce" would some how rub onto the Boston. I would rather see the Boston being judged on its own and being priced as such -- independent of its more famous cousin and without the associated price premium for any (mis)perceived relationship to Steinway. Drawing an automobile analogy, compare a Mercedes Benz and a Crysler: when a consumer buys a Chrysler in the US, the consumer never thinks that he is buying any Mercedes Benz design or parts, and would not pay more for the Chrysler than he would a comparable alternative -- no price premium for the Chrysler just because it's parent company also sells Mercedes Benz. (And, no knocking on the Crysler -- they make good cars too!)
Quoting from a book by D.W. Fostle (1994) titled "The Steinway Saga,"
"Not sharing proportionally in the growth of the grand piano market and beset by much cheaper grands from Japan and Korea -- the "piano-shaped objects" to which Bruce Stevens (the then President of Steinway Musical Products) referred -- the strategy was to enter what would once have been called the "commercial" piano business."... a new piano to be made by Kawai and called "Boston"..."When queried on the identity of the designers, Bruce Stevens stated that they were the engineers in Astoria [Steinway headquater in Long Island, New York]; that none of these engineers had ever designed a piano before was candidly admitted. They had, however, taken a one-day scale design seminar from an outside consultant and were adept in the use of computers."
Duplex scaling is today quite common in grand pianos (especially in the 6'+ sizes), most of the Eastern European, Japanese, Korean, and Chinese made pianos have it. While Yamaha and Kawai use their own action, you would find that many Eastern European and Korean grand pianos use Renner action (German Steinways use Renner as well but the US Steinways uses Steinway's own "accelerated" action). Wouldn't hurt to ask what kind of action is used in the Boston (could be Kawai's action, could be Renner). The "accelerated" Steinway action, double-crowned diaphragmatic soundboard, Hexagrip pin block, continuous-bent hard rock maple rim -- all these features touted by Steinway and vital to the sound and touch of the piano will likely not make it to the Boston. The computer-designed pear-shaped hammers in Boston could not have been in the older Steinways (early 1900's when Steinway built its reputation) because computers weren't used to design pianos back then. The pear-shape hammer may be a good innovation, but that's hardly the "Steinway special sauce." (Hack, I don't even think that today's Steinway uses computer-designed pear-shaped hammers or whether other companies also use them -- but I have to check.)
Piano scale design and component quality aside, workmanship of assembly is also very important -- after all, we're putting something like 8000+ parts, with 6000+ of which are moving/vibrating into a grand piano. And then there is voicing and regulation. I am not aware of any work force transfer where experienced Steinway workers from New York or Hamburg get assigned to build, regulate, or voice the Bostons in Japan.
There is much more discussion on the Steinway-Boston-Kawai triangle relationship on line if you are interested:
https://www.pianoworld.com/ubb/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=003448All said, Boston is a GOOD QUALITY piano (and I am happy for Robert/tosca1 that he found one he loves so much) - just not a Steinway. Whether or not all Steinways represent GOOD QUALITY or good VALUE is yet another subject.

Personally, I just place more emphasis on sound and touch than the name on the piano. I believe that the more different pianos one plays, the better an idea one will have on what kind of sound and touch one truly prefers and loves. As far as design quality, build quality, and longevity/durability of pianos go, a piano technician would be more qualified to comment. Whether or not chan ends up with the Boston GP156, I wish him/her luck all the way getting the piano he/she wants!
