They have mostly older stuff, but plenty of it is really good.
Cheers (11 seasons)
A show I used to watch if it was on. Watched a handful of stuff from the first season, and what stands out is the sharp, sharp writing. Really funny, observational stuff, a reminder of the kind of stuff 'the networks' used to do very well.
The Adventures of Sherlock Holmes (13 episodes)
Jeremy Brett is my favorite Holmes by far, and this original run features his best, most consistent work. Catnip for mystery lovers.
Masterpiece Mystery: Sherlock
But Benedict Cumberbatch's contemporary take on the iconic sleuth is a close second to Brett. I was primed to dislike this modern 'reboot', but the casting is brilliant and the story updates are fresh and creative while maintaining the spirit of the originals. My one gripe is Sherlock's addiction being downgraded from cocaine to nicotine- an annoying nod to the moralizing, puritanical present.
Arrested Development (3 seasons)
A show I tried to watch several times while it was on but couldn't get into. I recognized the quality of the effort, but it seemed too disjointed. I checked it out on DVD after it had gone off the air, and what a revelation. My prime example of a show almost completely ruined by advertising. What was an unconnected, ramshackle mess on teevee becomes a tightly plotted BAM-BAM-BAM screwball comedy on dvd (or streaming). Highly recommended, check it out even if (maybe especially if) you didn't like the broadcast version.
Lost (6 seasons)
Another one I didn't get into on teevee that's much more fun minus the interruptions. Whether you enjoy it or not depends heavily on your appreciation for ongoing conspiracy-tinged non sequiturs. What it reminds me of most of all are the old cliffhanger serials- if you don't mind the hero who went over the cliff in the car last week showing up hale and hearty this week without much in the way of explanation, Lost is for you.
The greatest, weirdest soap opera ever shown. David Lynch reigns it in just enough for broadcast teevee, to the benefit of viewers everywhere. Spot on casting and pitch perfect writing carry the first season of this one to the Pantheon of teevee greatness.
X-Files (9 seasons)
Before Lost, there was the X Files. At its best, fueled by sharp writing and the profound chemistry between David Duchovny & Gillian Anderson, it was tremendous. At its worst, it was Scooby Doo Joins the FBI. Happily there is far more good than bad. And with streaming, if you catch a dud episode you can just flip right by!
Twilight Zone (4 seasons)
And before the X-Files....
The pioneer of televised sf/fantasy. Uneven, but most episodes are at least watchable and its high points rank with the best teevee ever.
Futurama (5 seasons)
Another one I wanted to like but couldn't see the value of until I caught it without commercials. Fairly funny upfront, but much funnier with a few episodes under your belt. Great characters make for a great show.
After years of being available only via pirated tapes (or later, torrents) a mother lode of episodes showed up on streaming. They aren't grouped by season, rather annoyingly- as a fan of Joel & the Bots I find Mike better as a supporting player than leading man and seasons would make him easier to avoid. But that's looking a gift horse in the mouth and complaining about halitosis. They're on streaming! Watch them!