I only recommend this in case you miss the couples from Star in my Mind and Sky in your Heart. It's basically just a collection of cute moments between the couples.
Even though I couldn't fully appreciate the special episode because I didn't watch Sky in your Heart (nothing wrong with that series, I'm just not interested), it was nice to see the characters again as they live together and are happy. It's also very relaxing to just watch characters being in love without having to fear plot twists or angsty moments.
My only complaint about this is just that nothing much happens. Special episodes usually have some plot, even just a hint of it. "Our Skyy" is the proof that making a single episode with an interesting plot is possible, so the lack of time isn't an excuse. It's not a necessary thing, so I still rated the episode pretty high, but it would have been nice.