The biggest appeal for me was the funny one liners and innuendos between the two main guys, Robby and Hatchi. There's a wonderful mix of story, jokes, lessons, and character development. I fell in love with the show and characters for the fun and lighthearted atmosphere. If you want serious mecha animes then this isn't it, but if you're looking for something that's fun and easy to binge watch, especially more than once, then look no further.
One of my favorite characters was Mr. Yang, he's the default villain of the story, but you'll begin to see he's actually really nice and forgiving. He just wanted an excuse to chase after Robby.
If you don't like soft undertones and hints toward boy love then that's also something to keep in mind for this hidden gem of a show. I've had guy friends watch it and still have a good laugh so I say at the very least give it a shot before you write it off.