I've been making music for years and I often work with samples. Luckily, Ableton Live accepts .flac files. It's important to have high quality samples considering manipulating the sound (especially time-stretching) can easily alter its quality.
Unfortunately, it's still hard to obtain music in Flac format. Few online music stores offer tracks in that format. [1] It's maybe a marketing issue. Everybody knows what an Mp3 is. It also took me some time to learn that such a format as Flac existed. But it's also a size issue. Although the compressing algorithm is incredible, people prefer to download (legally or illegally) a 80 MB album rather than a 500 MB one, regardless of its quality, because they either won't hear the difference or just don't care. And considering iTunes doesn't support Flac (only their own Alac format that is even less known), Flac isn't meant to be widely adopted yet.
[1] http://en.wikipedia.org/wiki/Comparison_of_online_music_stor...