Apple has done it with the iPod and its companions iTunes and iTunes Music Store. However, there is one customer that will never be.
That probably needs an explanation, given Apple's current market share both in MP3 players and online music sales. But first let me start by describing the really good things about their products.
The good things
It's hard for anyone to come even near Apple when it comes to design and usability. I've tested the Pods of my friends and colleagues, and it really is no sweat handling. The accessories available, both from Apple and third parties, are also brilliant. FM transmitters, AirPort Express, and remote controls, to name a few. And they didn't mess up like Sony, which betted everything on ATRAC as the only format.
iTunes is very well designed in comparison to other software I've tried, and works very well in drilling down to the music you like to listen to. It's also maintained by a very creative team. For instance, older versions used to suck at handling duplicates in your library. Now they've fixed that. In the next version I expect the duplicate handling to be even more automatic.
But there are showstoppers.
The bad things
No Ogg Vorbis support. For me, this is major. I rip all my CDs using Ogg, to ensure my freedom. AAC is completely closed, MP3 patent-encumbered.
There does exist hacks to make iTunes play .ogg, but they never worked very well for me (on Windows).
Closed Platform. Not that it has really hindered cool third (and fourth) party stuff to appear. mt-daapd is a good example. Searching for iTunes or iPod on freshmeat.net also indicates that the platforms are hackable.
But why won't Apple open it a bit more? It would only increase Apple's position in the Open Source / Linux world.
Music synchronization. I own several computers, and use even more. I have music on more than one of them. One is at home, serving music to my KiSS DP-500, in addition to serving them via mt-daapd. Another one is also home, but running Windows XP. It has iTunes and Windows Media Player, and can play the music from the Linux box. It does not have any music stored locally.
But then there's my laptop. It also has iTunes, and a lot of music. Keeping the two music stores in sync is a pain. iTunes does quite a good job keeping my music folder organized by artist / album, but it sucks at handling merging without creating duplicates. If two tracks have same artist, title and album information, but different genre, iTunes considers them as two separate songs! You can fix it with the Edit / Show Duplicates command, but this is a manual task after all.
There does exist a third-party utility for synchronizing two iTunes libraries. Take a look at syncOtunes.
The ugly things
Apple Lossless. We already have FLAC. Apple Lossless is simply un-playable on platforms Apple does not support.
AirTunes. This could be a brillant platform for wireless transport of music in a home cinema environment, hadn't Apple crippled it with encryption and only supporting Apple Lossless files.
DRM. This isn't Apple's fault alone, but an industry problem. But they do currently use DRM as a way of locking iTMS customers to iTunes and iPod. Luckily PyMusique solves this. What Apple should do, is cooperate with standards bodies to create interoperable, "open" DRM schemes. Instead they attack the ones trying to pry this open, be it induviduals or corporations.