April 12th, but it looks like you can now order a Zune HD 64 nonetheless -- straight from the Zune Originals website, at least. As expected, the device runs $349.99, and the 16GB and 32GB models have now also been knocked down to $200 and $270, respectively -- all of which are naturally available in the usual range of different colors, and with custom designs for an extra $15. You'll also, of course, get the latest v4.5 firmware pre-loaded on the device, which packs new features like SmartDJ that Microsoft was recently kind enough to demonstrate for us.
[Thanks, Henry and Jonathan]
Update: Turns out the Zune HD 64 won't come pre-loaded with the v4.5 firmware -- you'll be prompted to download it when you connect the device.