When you say that this firmware upgrade (2.01NA) is for B hardware, is it also for B1 ?
Is B1 and B hardware the same ?
Yes, at least on the D-Link United States site, when you want to download firmware, it only presents you with two choices, DIR-655 and DIR-655_REVB. If you choose the first link (REV A), there is a single choice regardless of what revision level of A hardware that you have, same as the downloads for REV B. I went to the UK site, and I noticed that they don't hae REV B listed as a choice for firmware downloads. However for each of the four A revisions, there is a separate page for downloading firmware for each hardware revision. However, I have verified that (at least for the most recent version of the firmware) the downloaded file for each A revision level is IDENTICAL. I think the only reason there is a different page for each revision is because the product page is organized differently than the U.S. ones, with all support resouces (product manuals, fact sheets, etc.) on a single page with the firmware.
Since there are in fact diffrences in hardware between each hardware revison level, my guess is that the firmware is sort of a "unified" firmware (much like NVIDIA video drivers) that has information for all revision levels, but it only applies the needed changes for your specific revision level.