I KNOW they knew about the performance issues prior to release, because these issues have existed since early in the EA stage. And what is Unstable (and even every stable build prior), if not player testing? They have known, for a very long time, that the game was performing... Let's charitably say "sub-optimally". Now, if you're going to say that they can't fix it if it doesn't happen on their computers? Well, then, I guess we should never expect it to be fixed. Ever.
On SOME people's computers. My computer, on the other hand, has run it fine. During Early Access, sure, 45 FPS was the norm... but they fixed that in the 1.0 release (in fact, they had the fix on Nightly a couple weeks or more before the 1.0 release). In THAT case, my computer did 60 FPS easy, unless I was standing in front of the door next to Esther when it's open. That animation is a MASSIVE framerate hog, lol. But it's isolated to just THAT spot in the game and nowhere else. The people having the issues need to be more specific and run more tests, and do more. Simply saying "MY FRAMERATE SUX! FIX IT NAO!" does NOT help you, nor CF. You need detailed information, like actual framerate numbers, lists of hardware and models ("My CPU is _____, my HDD is _____" etc), and driver version numbers for all of your hardware. You, and other people like you experiencing lag need to compare hardware and driver and OS versions until you find some kind of common ground. Also be sure to include what other software is running in the background, too. And for that matter, try killing all unnecessary software before running SB. Try disabling constant scanning from your AV software (you don't really need that if you're not browsing the net or downloading) to see if that helps things. etc. etc. etc. But I don't really see much of that going on, I see "My framerate is low. Why haven't you fixed this yet!?". But yet other people with weaker computers have frame rates that are just fine. That points to a problem with the person's computer, NOT the game. If it were the game's fault, then EVERYBODY's framerate would be tanking. Me, and many others, have no problems whatsoever.
Few mistakes on your part. 1. You are assuming the performance issues way back in the Koala days is the same problem that is being experiences now. This is unlikely because their engine has gone under several big changes since that time. 2. You are assuming that because it may have been known about in Unstable, they should have known what the problem was. You are forgetting that they need to be able to reproduce the problem before they can properly fix it. Can't reproduce, can't fix. If you were not assuming that, then what is the point of that statement? Sure, they knew of a problem. What then? 3. You are insinuating that the performance issues effect everyone. It isn't. The majority of people are performing just fine. Anecdotal evidence from myself, I have played the game flawlessly on about 10 different computers over the course of the last year and a half. It is reasonable to say that the game has been performing just fine for Chucklefish and their systems. Again, can't fix what you cant reproduce. 4. Very "black and white" of you. A nice Fallacy. Not expecting it to be fixed is very rash, but the chance of a fix does sharply fall if they can't reproduce it. There is always the chance that they could stumble upon the issue themselves, or maybe in their various engine changes they inadvertently fix it. We won't really know.