I don't have to worry about having something CPU-demanding (like a streaming Flash player in Chrome) running on the TV while trying to compile on my work laptop neither one will cause choppiness in the other.It's a bit of the feeling of having a second (big) monitor hooked up to your computer (or using Apple's AirPlay "extend display to this monitor" mode in OSX) but having the two be separate computers is actually a good thing, frequently:
You don't ever have to pick up a remote, or try to get Bluetooth peripherals to work over an 8' distance you just flick your mouse up "past" the top of your laptop screen, do a few things on your TV, and flick back. If you frequently sit in front of your HTPC-enabled TV with a laptop, connecting the two together using is amazing, UX-wise.
It would be really neat if I could, say, choose Star Trek TNG and get an automatically generated list of the best 10 episodes (with data pulled from thetvdb, IMDB, etc), or if I could go into Movies and choose an option to group movies by randomized Netflix-like specialized genres. It's a neat use of metadata, and it would be interesting to see it go further. Similarly, the TV screen has groups for recently aired TV episodes, and even has shows grouped by the channel they're currently airing on (!).
If you actually go into a movie and open the Extras menu, along with trailers/features (if you have a Plex Pass), it'll show you other movies by the same director and with the same lead actors. It looks like the Movies screen will automatically offer up unwatched movies with recent release dates, as well as groups of unwatched movies from the same director ("Top movies by. The most interesting new feature to me, beyond the UI itself - there's now some algorithmic generation in the movie/TV screens. On the other hand, Plex has way better device support and while you can get transcoding to/from devices in Kodi, Plex is a lot better at it most of the time. On the other hand, if you just have random files that are scattered about or organized by folder or perhaps named differently then Kodi works a whole lot better because it just lets you drill through files on disk (it has a library too, which is functionally about the same as Plex and suffers from similar drawbacks). So in other words, if your files are reasonably well organized and named following one of the conventions recognized by Plex then it does a pretty amazing job organizing and scraping. They outright do not support directly browsing files AFAIK. It'd always mis-recognize files or they'd be completely missing even though they were on disk. My experience trying several times since Plex came out (most recently last year) is that this is extremely unreliable and wonky. You can subsequently choose to view files by "folder", which doesn't actually browse the filesystem directly but instead looks at the database to see where the file came from originally. If you follow their naming scheme with your files it does a great job pulling in metadata and such, but if not it doesn't do so great. The Plex server doesn't really browse the filesystem, it scans folders for media files and then parses the names.
Actually, it's really not good at handling that sort of thing in my experience.