I used to watch this show years ago, back in the day when George Clooney and Noah Whyle still starred the show with Laura Innes. I was pretty young then, but I remember watching this with my mom late every Thursday night.
I have seen glimpses of the show afterwards, these last few years, and although it didn't hook me, this is definitely one of the best hospital shows there is.
The personnel is interesting, there is drama between them and in their lives, but still the hospital life itself is given room to flourish.
While I'm sure there are many medical inaccuracies in this show - like in any other such show - they make ER believable, and in the end that is what guarantees a hit show, which this one definitely is.