I thought Mission Hill was a step in the right direction with Gus and Wally. Yeah, it wasn't a perfect attempt, but the writers definitely got some things right by not making their homosexuality the focus of the two anytime they were on-screen, while at the same time treating their relationship as normal (if slightly dysfunctional- see "Andy and Kevin Make a Friend" when Gus refuses to take the knife out of his head), not some sick abomination, odd novelty, or morbid curiosity. They're just two older guys who happened to be gay.
And you wouldn't even know Gus was gay at all, because he doesn't exhibit the stereotypical fruity gay behavior that is so easy to write, yet so tired and (many times) inaccurate.
Additionally, "Plan 9 From Mission Hill" was a good window into Wally's personality. It shows the writers didn't treat him like a caricature who makes a few double entendres and leaves. They wanted to explore his backstory, and how that related to Kevin's growing love for classic cinema.