Killing off characters like anything has pros and cons. SG:A killed off at least two of it's leads Beckett and Weir, was it a good move that's open to debate. But in the case of Beckett the fallout was so bad they had to bring the character back (via a clone).
I actually like Stargate Atlantis but I never saw the point in killing off those two characters.
I loved Beckett's death. Possibly because I somehow managed to be totally unspoiled for it so it shocked me. I got teary. This happens so rarely that I was quite pleased.
Elizabot, glad to see her go. Terrible acting, AWFUL.
And really how well did it work out! We got Beckett back, we got Kaylee and we got Bob Picardo.