In iTunes 11 the user interface has been completely redesigned. The interface makes better use of your screen real estate. The main view is all your albums represented by their album art and the album name and album artist just below. This is a great view for browsing through your library. If you fancy creating a playlist the interface is far better. You get much more room to see and organise all your playlists as the sidebar which they used to sit in has been hidden. If you miss the sidebar in iTunes 11 just click View > Sidebar, but it's really not needed anymore. If you drag any song/album/artist you can drop it into a playlist. The list of your playlist pops up whenever you drag anything. It's easy to drop onto your iPod, iPhone or iPad in this way too.
Once you update to iTunes 11 your library gets updated but this was painless enough. Some of the new features require you to share the album details of your library with Apple, but this was an easy decision to make as an iTunes Match subscriber. The new features include showing you galleries of artist's and links to related music.
For the full list of the new features click read more below.