Meh... You get PBS which is really way more interesting than Discovery/History/Science channels have been in ages IMO.
I wouldn't say there's an equivalent experience ATM if you ditch cable unless you're willing to break copyright laws. That being said, I get along just fine with my Roku + Netflix + Plex on my mini. The Roku is mainly for renting movies on Amazon, since iTunes doesn't seem to offer every movie that's available in HD in HD on your non-iPad/AppleTV device which is pretty lame. I was doing a good amount of iTune rentals until I got my mini and noticed most of the stuff was not available in HD on it. Amazon gets my business now. Oh well.
Using the mini as a media center with Plex, I get the Daily Show, Colbert Report, South Park, Khan Academy, NPR, CBS shows, PBS (good documentaries), and a crap ton of other things for free. You can also use it for Netflix (but it doesn't do HD, so I use the Roku for that), Amazon (if you're willing to fiddle with the plugin), and Hulu.
For shows I like on HBO and Showtime (Dexter, True Blood, Hung, etc) I have to download them via torrents to watch them during the current season. Most of the time I just buy the seasons later on iTunes or DVD to say I spent money on them, but I only keep the torrent downloads for watching because the quality is better and there's no DRM. iTunes was doing "season pass" for some shows, and I gladly paid for that. I was only watching two shows at a time then anyway. But since the only way to watch shows as they come on anymore is to shell out for cable service or pirate, well, the choice is easy for me. I find paying a large sum of money every month when I only enjoy maybe 5% of what I get for it annoying.