The workaround that I use (especially with the $#!+ - slow HR21) is to keep "manage recordings" handy in the "back" button queue. This also helps with other menu functions, as I'm already a few button pushes deeper into the menu and avoids always having to reload the posters at the top of the menu. Simply "exit" at the point you want to keep, and then use the "back" button, gaining quicker access to whatever function you want to use it for.
The trick is you have to get in the habit of using the "back" button rather than accumulating funcions via exiting out of things (such as "guide" and "list) in order to keep the queue from getting too long. Also, it seems to get lost sometimes when deleting a program at the end rather than from the playlist or info screen. Of course, you'll still have to load it initially upon powering up (also the first thing I've gotten in the habit of doing).
All that said I, too would also much rather have a dedicated function button.