This episode is necessary, but that doesn't make it good. Mostly, it is a response to the Season 6 finale -- primarily Leo's admitted infidelity. Grace deals with this by stealing his things -- a childish response for a woman of her age, which is mostly chosen for the humor but ends up coming off flat. Will contrasts her by being whiny and shallow. Unfortunately, Jack and Karen aren't that much funnier -- the Jennifer Lopez storyline with Karen's song is flimsy, uninteresting, and seems to be an excuse to give their characters some screentime. But they aren't at their best in this episode. None of them are.
Which isn't to say that this episode is without its moments -- one of Will & Grace's strengths as a sitcom, I think, is its ability to take serious situations seriously, however funny everything else may be. Infidelity is definitely a serious issue, and despite the humor in the stealing scenes -- when it comes down to it, and Leo and Grace actually have their standoff, it is a serious conversation as is befitting a serious situation. The end, It's funny, too, at times, the final dinner with Leo, Will, Grace, Jack, and Karen, while not flawless, is hilarious at times, and the kabbalah scene at the beginning is humorous as well, as most scenes are where Will plays the voice of reason to everyone else's measured insanity. FYI: I Hurt Too is weak for Will & Grace, but for quite a few other sitcoms, it could be counted as one of the genuinely funny episodes.