iTunes Store features:
First, I'll be discussing the two features that I probably will be least likely to use, but still bear mention. iTunes LP is a great step forward in the field of replacing hard copy CD sales in my opinion. Album art, Liner notes, and Lyrics (which hopefully will be automatically added to files) are great additions that could prove a turning point in how some people buy their music. Extras for movies could similarly prove to be a turning point feature for some peoples movie purchasing.
Neither will change my buying habits much at all simply because of my preference for getting a hard copy of media I purchase. They are closer than ever before to the point at which I switch, but I'm a stickler for the physical copies of my DVDs and music.
Aside: Just in case you are a person who purchased things using the Shopping Cart be aware: it isn't there anymore. It's been replaced with wishlists, see this TUAW Article for details.
Genius:
I've liked the Genius feature since I tried it for the first time. However, I've always had one minor problem with it, the playlists it created were too short and so I heard them over and over again in many cases. iTunes 9 fixes that for me. Genius Playlists now have a length that can be set at 25, 50, 75, or 100 songs. This is a great thing in my opinion.
Another new feature in this version is Genius Mixes. They look promising, but I haven't had the chance to play with them too much yet. They look like they may be a great addition simply because they will keep playing without me having to intervene at all for the duration of my listening session. I'm not sure how you "seed" them or select what their themes are at this point however so it remains to be seen exactly how useful the feature will prove.
Smart Playlists:
Smart Playlists just got smarter in iTunes 9, with the inclusion of a trick from Finder's Smart Folders. Smart Playlists can now include multiple sections broken up with their own criteria, for example the Classical Music playlist that I found added to my sidebar when I launched iTunes 9 for the first time. Using this ability I was able to merge what had previously been 3 playlists I used to make sure my music had all the proper meta-data set the way I wanted it became 1 playlist, and 2 playlists to control the syncing of my Nano became 1 playlist.
Syncing:
This sounds like a good time to talk about the changes to how syncing works. Now instead of just being able to sync using playlists you can tell iTunes to sync all music by artists you select, all music within a genre, and playlists you choose, all at the same time. This is something a lot of people had been using Smart Playlists to do for a while, and now it's built into the core feature set. I'm told photo syncing has been improved to interact with the '09 version of the iLife suite, ie Faces and Events, but I can't confirm this as I don't have iLife '09 to test it out.
Sharing:
Home Sharing is a feature that I probably won't take too much advantage of, but it's certainly useful if I choose to. Being able to share music within a household is something that I'm of the opinion shouldn't be made difficult, and it would seem that Apple agrees.
Social Media sharing seems to have come to the Store, at least in some respects. iTunes still lacks the sharing feature that I would like, but am well aware is unlikely to ever happen: integration enough with Facebook so as to show what's been played recently by my iTunes from within my Facebook as I currently do with iLike. I'm understanding that it is unlikely because it means Apple would have to either acquire iLike or make a Facebook app duplicating the functionality, neither of which is likely. Frankly, that's fine with me.
Final Thoughts:
For the price it's a really great upgrade. It fixes some annoyances I've had because of the way in which I use iTunes, and made those things much easier to do. I still can't search for music based on whether or not it has artwork or lyrics associated with it, but those are probably not features that the average user would have a need for. I like the changes to the appearance of the player and the store, though my gut tells me that the search for podcasts is less flexible than it used to be, I suspect my gut is saying that under the influence of a quesadilla.
