I love Flac, and would rip everything into it, if I could.
I don't like the way websites simply offered MP3's at 320kpbs or less, and get you to pay as much as it would a CD version that is a lot higher quality.
You may not of heard of a format called Ogg Vorbis, but it is better than MP3 at lower bitrates, and sounds better to me at higher bitrates too.
I tested between a FLAC and a OGG Vorbis (both free codecs) file, of a Genesis song called 'Firth Of Fifth', with the Ogg Vorbis at a much higher bitrate than you can get with MP3, at 500kbps.
Now, using a piece of software called ABX, which allows you to listen to two sources and compare them, and has a feature to test how well you can hear, with random X and Y tests, I managed to hear a difference between the FLAC and the 500kbps Ogg Vorbis.
It was noticable enough, that after 17 tests, I had only gotten 2 wrong, and had achieved a guessing rate of 0.1%