Miro is program guide, media library, downloader, media search and player all in one. Program guide doesn't show when something is on, as it doesn't matter. Instead of that it has small scrolling list of featured shows (or channels as Miro likes to call them), one example category, popular shows and new shows. Miro likes to call shows channels, but mostly you can subscribe to one show at a time. It's quite rare to have more than one show in one channel. If channels are meant to be similar thing as TV channels, that is.
One additional category is recommended videos (you need to create account to use it though), which recommends new shows based how you rate shows. It's not perfect, as it recommends stuff in foreign language and some shows that based on description won't most likely be that interesting. But it's one additional way of browsing available shows.
Most of that stuff is available as channels too, so it's possible to just subscribe to some category and stop thinking about what show to subscribe to next and just press play and watch shows. Miro doesn't do streaming though, so you have to wait for first show episode to download, but after that you can start watching more or less uninterrupted if your connection can download episodes faster than you can watch them.
That brings us to downloader, which has some nice features. When you subscribe to a show it starts downloading right away. By default it downloads just latest episode of the show and after that all new episodes when they are available. It's possible to change channel settings to download all available episodes too. By default it doesn't download more shows if you have three unwatched episodes, so your disk doesn't fill up immediately. Which will happen soon anyway, even when Miro does pretty job cleaning things up.
Yes, Miro knows how to keep things clean. It deletes videos after you have watched them, so you don't have to delete them by yourself. By default it keeps watched video for five days, but it's possible to tune it from 30 minutes up to a month. You can also save video to prevent automated deletion.
There's also limit for simultaneous downloads, which is great if you want to get start watching downloaded episodes rather sooner than later. It seems to get confused though if you pause and resume shows and starts more downloads than the limit. If that happens, you can try pausing and starting downloads again, which might put downloads back to the queue.
Miro also supports BitTorrent, so actually anybody could start distributing their own shows, without paying high fees for servers. It's quite easy to use for example sites like Legit Torrents for distributing the files, so there's not really anything that prevents distributing your shows in high quality and without any limits on video length. Still more work than using Youtube, but at least possible.
You're not limited to using program guide, as it's possible to add any RSS feed as channel or download any file.
Search is also nice addition. It searches videos from few different services (including Youtube) and it's possible to download search results without any hassle. Only downside is that as Miro doesn't do streaming, as I mentioned already. But you can keep the downloaded videos.
Technology behind Miro is based on standards. Channels are just RSS feeds, so it's possible to use them in other programs if you want. Miro just wraps everything up nice package, it doesn't actually do anything that hasn't been done already. But if Miro encourages getting more RSS feeds out there to subscribe to, it benefits other similar programs too.
What Miro is not suited for, is for using it with remote from your sofa. It's bit limited even with regular keyboard. That kind of interface would make Miro be able to complete with all media center programs out there, with advantage of having huge library of free media.
There's surely some stuff I forgot to mention, but with such full featured program, it's quite hard to remember to cover every feature. Miro has it's flaws, but all the embedded components work together in a way, that wouldn't be possible by using individual programs. Though on the other hand, using full featured media player (embedded player has some limitations on supported video formats for example) instead of the embedded one would be nice, but that would mean that Miro can't know if you stopped the video half way through and continue next time from same place. Also embedding Firefox and programming in Python makes Miro quite resource hungry application. But despite that, it's just hard to justify getting rid of it as everything works so well together.