I bought the first season on a whim one day because it was like $9, so I figured I might as well. I liked the show well enough, the weird medical cases make the show for me, and I enjoyed the second season. However, I only have season one on DVD and I haven't liked the show enough to buy any of the other seasons.
I stopped watching halfway through the third season. The show is just too much of a typical soap opera, and the fact that the cases always reflect the doctors' stories bugs the crap out of me. It's acceptable sometimes but every single episode? This is one show I'll never be hooked on, and I think it's completely overrated.
Once the fourth season comes out on DVD, I may try to start over from the beginning and see if I can get back into it, but that depends on what shows are on at the time. If the strike completely kills pilot season I probably will.