You may want to take a look at ATOK IME, they have versions for Windows, Mac, and Linux and is preferred by most Japanese typists over the built-in Microsoft IME for many reasons
http://www.atok.com/Well the FILCO Tenkeyless with Blue Cherry switches is well liked around here, but it is only available with the ANSI layout. I mention this because even if you're typing in Romaji, there is still a benefit in using a Japanese layout keyboard, as they have 4 keys dedicated to IME control, so they simplify the task of moving in and out of the different IME modes. An ANSI layout keyboard will require the use of hotkeys and the mouse to choose your modes. It is worthy to note, the Japanese layout does have different locations for some punctuation and a larger "ISO" Enter key, which may throw you off a bit if you're rearranging a board for Dvorak, but the Japanese layout keyboard model I'm offering in the classifieds is the only one you're going to find available with Blue Cherries. Only a small number of these were made and they are no longer produced or sold.
As for how well a Blue Cherry board holds up against a BS board...if you're talking about driving over it with your car, the BS board will win, but Blue Cherry switches are lighter to the touch and less work for long periods of typing. The sounds these two switches make are different as well; both are reasonably chatty, but a BS board is definitely louder, so you'd want to take your company into consideration as well.