I find "cis" useful, personally. I'm bisexual, so certainly "straight" isn't applicable. In a lot of contexts I'd use "cis" to refer to myself, I suppose "not trans" would also work, but it'd be clunkier.

Plus, there are times when the thing I want to centre in my communication is the cisgender perspective that I have. For example, I was recently discussing with a friend that seeing trans friend's gender euphoria improved my own relationship to my gender because it made me ask myself whether cis people could experience gender euphoria and if so, why couldn't I recall any instances of experiencing it?

I feel like the term "cisgender" implicitly acknowledges that voices and experiences like mine are important in building a shared understanding of gender — i.e. trans people aren't the only ones who have a gender. Like, obviously I can't speak directly about trans experiences, but that doesn't mean that I'm expected to shut up and contribute nothing to the wider conversation.