Personally, McKay is my favourite character on Atlantis, so I watched his first appearance as a character with interest.
Mostly, there are a lot of differences between his Atlantis character and the one that shows up in this episode. In Atlantis, he's taken on Carter's role: the scientist responsible for making things happen when guns won't do it. Also, Atlantis pokes around in his personal life: His various illnesses and his sister (whenever McKay's sister shows up, Atlantis has a good episode) show that he has a human side and a heart, despite his obnoxious exterior.
While McKay of SG1 is obnoxious , not much else about him in this episode (at least, that's important) is similar to McKay Atlantis. McKay SG1 is a naysayer who can't be bothered to make anything happen, an chauvinist, and even a little bit stupid scientifically (but that's compared to Carter, of course). The seeds of the later character are there, of course: He IS funny at times, he likes to eat (especially in stressful situations) and is afraid of lemons.
For me, the episode was mostly interesting as a McKay character study. (I'm fascinated by watching characters change.) However, all of the usual SG-1 characters play their roles well, and I enjoyed seeing more of Maybourne in his unofficial "rogue agent" role (much more likable than his official role). While there's not a great deal of character development, the episode advances the plot nicely and is a fun way to spend an evening.
