Arguably the most effective Deep Space Nine episode created to try and make it attractive to fans of Next Generation, the title already says most of the reason why, because it features Q.
The funny thing is, Q almost doesn't even notice that he's on the space station, because he's too busy obsessing over the other crossover character, Vash (I would argue this as being her best appearance in the franchise, possibly because that romance with Picard never really made sense and clearly was going nowhere fast), and mostly reacting to the actual main characters of the series as distractions.
His best encounter is with Sisko, though, and "Q-Less" as a result has the essential Sisko moment of the season, outside of the pilot, in which Q foolishly engages in fisticuffs with the commander, and gets to utter the line, "You hit me! Picard never hit me!" While Patrick Stewart successfully converted Picard into an action star later in Next Generation and in four movies, Sisko was already more physical in his first appearance than his predecessor ever was, willing to get down and dirty (even when reluctant about it, and rarely needing Klingons to provoke him). It wasn't even in a strictly physical sense, since few Star Trek characters (aside from Kirk, and everyone in 2009's Star Trek) are very mobile, but more in the menace in Sisko's eyes, knowing that his was a kind that was always working, not just out of necessity, but because he was always refraining from hitting someone (making his mirror universe counterpart more appropriate than most fans probably realize). Yes, he hit Q!
A lot of fans complain that "These Are the Voyages...," the final episode of Enterprise was hijacked by Next Generation. The same can be said for "Q-Less," except both episodes say far more about the series they're actually in than the guest characters who supposedly steal the show. This is about as far from a typical Q episode as you can get. As I said, he spends most of it obsessed with another guest character, which is far from unprecedented, but without going out of his way to cause mischief. Like "All Good Things...," rather, he's not the cause of the mischief, he's actually trying to prevent it. It's a grounded Q, even more than the time he became human, and it's very Deep Space Nine. Most fans dismiss this appearance, probably for the very reasons I've just explained. I argue that they make "Q-Less" essential.
As an episode of this particular series, it's one that helps put things back in perspective, perhaps for the first time since the pilot, pulling away without losing focus, but rather gaining more than it seems.
It's one that definitely deserves another look.
franchise * series * essential * character
John de Lancie
Memory Alpha summary.