I really applaud the writing staff's decision to kill Jimmy.
It seems like there are a few different camps here when it comes to criticizing this show. Those who dislike certain developments because it goes against whatever preference they have and those who dislike certain developments because they think they are bad writing in terms of continuity or mechanics.
I like Jimmy too, but fuck, it's not really affecting to lose a character that's written so no one gives a shit about them. Plus, considering how integral Jimmy was believed to be to the show, having him die serves a really great purpose in terms of mechanics. You now know they are willing to kill off main characters. This creates REAL tension.