I started moving over to FLAC last year when I got a new MP3 player. With storage being much cheaper it was possible to store a decent amount of lossless audio on a single device. I actually find that the difference is especially noticeable when driving. I'm not sure whether it's a dynamic range thing or what, but I'm able to listen at a much lower volume without the car noise onscuring the music than when playing MP3s.
When listening at home it's not so obvious, but MP3 can sometimes introduce unwelcome and disturbing artifacts. Even on a far from "hi-fi" setup, I was listening to "Equinoxe" a couple of days ago and had a big WTF moment. I'm pretty sure it was a 192kbps file but it's since been deleted and replaced with FLAC.
Does anyone remember Barry Fox in Hi-Fi News & Record Review claiming that you could get better quality audio from a CD by using a green marker to draw around the edge of the disc? That was the day I never took any articles about audio seriously again. Even when it correlates with my own opinion I have to double-check! :-)