"Not available" meaning you refuse to make prior versions available to your customers?
I purchased a brand new DNS-343 in mid December that shipped with 1.01. As 1.02 wasn't available until late September 2008 I didn't consider it at all unusual that mine shipped with 1.01.
In early January I made the huge mistake of updating my unit to 1.02 (my bad for thinking ADS support actually worked!). Come to find 1.02 has other issues as well (as I have relayed via threads). In short, I experience lock-ups and other quirky behavior with 1.02 that did not occur with 1.01. While 1.01 may not have been "much better" (as you say) than 1.00, it was certainly better than 1.02, at least for me.
It's no secret that there is issues with every version of firmware for this device. As such, what's the harm in D-Link making every version available it's customers, despite their particular quirks? As with any device, some firmware versions may work better for some end-users than others.
To not provide your customers with a downgrade path to a currently shipping version is truly ridiculous!!