Unfortunately, there are no alternatives at this time. You're stuck with whatever DirecTV provides. As you note, a new high-definition DirecTiVo is expected early next year.
If possible, you might try to find a HR20 as a replacement. The HR20 is somewhat more responsive (less laggy) than the HR21/HR22/HR23.
If possible, you might try to find a HR20 as a replacement. The HR20 is somewhat more responsive (less laggy) than the HR21/HR22/HR23.