When I first started watching, I watched a little of both shows and got attached to the SGA characters immediately and didn't like SG-1 anywhere near as much- but when I finally buckled down and just watched SG-1 I came to prefer it- so yeah, for an SG-1 fan it was cool to have Carter come to Atlantis. But in the end I didn't think she worked as well on the show as Weir. If you've seen even a few episodes of SG-1 you probably know that Carter was basically a technological miracle worker, and they really had to dumb her down to keep her from stealing McKay's show- whereas Weir had her own skillset that no one else really filled, so that never happened with her.

And I absolutely get why anyone watching Atlantis who didn't really care about SG-1 would be bitter about what happened :)