I personally have a Model 622 from Dish Network and I love it. There has also been talk about supporting an external HD for additional archived storage so you don't have to delete stuff when the main HD gets full, however, it isn't available yet.
There is a company called Nextcom that can legally mod your satellite or cable receiver provided that you own the unit. The mod allows you to be able to transfer HD content in HD from your receiver to a PC which you can then transfer to whatever media you like.
I know this doesn't solve the issue with having to pay extra for the right to record stuff because you're still paying for your sat or cable service, but it does allow you to archive Hi-Def recorded content.
If you want to check it out you can go
HERE NOTE: I have no personal experience with this mod, however, one of the guys that posts regularly in the St. Louis HD AVS Forum has one and loves it.
EDIT: I guess I was leaving it up to you to assume that I meant you could off load Hi-Def content and not just SD stuff. I've adjusted my post above accordingly.