"Gender Bender", the only X-Files script ever written by Paul and Larry Barber, is a mildly interesting mediocrity. There's some cheesy scenes and a silly plot, but it never becomes aggravatingly annoying as several season one episodes do. That doesn't mean it's particularly good either. The script is bland and flat, but I simply do not see what so many people hate about this episode, outside of the overused 'dangerous succubus' angle. The ending doesn't work as we learned more about extraterrestrial life later on in the series, but it worked at the time as a sort of Twilight Zone twist on things.
This episode is notable for two reasons: Nicholas Lea makes his debut, not as Krycek, but it's still the first episode he was in, and frequent X-Files director Rob Bowman makes his debut. One of the reasons this episode gets a 5/10 from me instead of a 4/10 is Bowman's work. It's always good, and it was the start of a working relationship hugely beneficial to Bowman's career and to The X-Files' visual aesthetic.
5/10