In short, your reply reads as if you haven't read my lengthy dissection of the Recall Knowledge rules and how they are both hyperexact and hypervague at the same time.
I invite you to address my points directly (preferably over at the linked thread), but if all you want is to dismiss my findings without more than your opinion to base it on, then I'm afraid I'm just not interested.
Sadly, after a few interesting comments, that other thread devolves into what one poster called "pomp and overwrought hand wringing", so I can't say it goes very far in encouraging thoughtful discourse.
This said, in actual play, so far, we haven't encountered any significant problems with Recall Knowledge checks. Yes, in combat, they eat an action, so players are not choosing that option very often. Yes, in many cases players can use Recall Knowledge outside of combat, so the one-action cost is irrelevant. If the PCs can scout whatever strange critters they're about to face from a nearby hilltop, they could certainly call for Recall Knowledge checks without any meaningful action-based cost.
Indeed, in our current campaign, these checks happen most often outside of combat, when players are investigating clues and trying to wring additional information out of the bits and bobs they've discovered. It's seemed very useful for me, like a
built-in delivery mechanism for information that I as the DM want my players to have. The fact that the players are actually
asking for information instead of just soaking up a lengthy DM monologue is just spice for the pudding.
If we're restricting the discussion to using Recall Knowledge on critters in combat, I still fail to see the problem. Sure, the DM has to make up interesting tidbits to feed players' successful rolls, and misleading tibits for critical failures, on the fly. That's not hard to manage. I tend to think about what sort of character is making the check and how he would have come by the information. Maybe a scholarly PC recalls having read about this critter in a book of lore. Maybe a PC from a small village recalls hearing "The Legend of the Mean Bandershatch" at the knee of Old Man Bart when he was a kid, or some traveller telling about his narrow escape from the Crypt of Naughty Secrets down at the inn.
Most times, though, I don't think the DM needs to give it much thought, since the focus is on keeping the combat flowing quickly. I'll just reel off "It is said that the worm-like ankhrav disolves his foes' armor with its acidic spittle," without taking a 30-minute pause in the battle to describe the old bard Persnickety singing the "Ballad of the Acid-Drenched Knight" to a full house three years ago last Tuesday.