Suffering from the old age can't sleep crap, I checked 2 of my HR24s this AM, about 5:30AM - no joy. So I forced the download and 0x57B which is the newest.
For those impatient ones, here's a link to a site to tell you when the various versions are in the stream. Note all times are Pacific Standard time.
DirecTV Firmware Watcher
If the version you are looking for is in the stream, it should download with no problems. It did for me. One note that I've been reading about is that sometimes the cache clears with this software (most of the time), and sometimes the cache won't start refilling very quickly or at all. If that happens, just reset 2 times within 30 minutes and it will clear all the cache and start refilling it.
The HDGUI is basically nothing more than a nicer looking screen of all the stuff you are used to in a slightly different format. The high contrast and better formed characters make it easier to read from across the screen, but I never thought that it was difficult to begin with. On my HR24s, since they were just updated and are refilling the cache, I don't really notice much of a speed difference and frankly didn't expect much of one as the HR24s aren't the pigs that the previous HRs are with the older software.