How does Plex work nowadays?
works great.
plex now uses a client / server model.
the server works on windows, mac and linux.
the client (player) works on windows, mac, iOS, android, roku, jailbroken aTV (so a 2), and some LG and Samsung TVs.
-you can watch in a web browser, so you can use linux if you wanted.
you can run the client and server on the same computer.
if the client isn't capable of playing a certain media file, the server will convert it on the fly as you watch it. So you can have an uncompressed blu-ray in your library, and play it back on any of your other devices. and if you have a decent internet upstream connection, you can even watch away from home over the internet.
and you could start a show on one client, stop, then change to any other client and pick back up at the same spot.
they also have to ability to sync files to your mobile device so you can watch offline.
(currently in paid beta, and only available with iOS)