The park could've brought Premier back in to update the LIM's, but by that point they had already sunk a lot of money into trying to fix the ride. This included reprofiling the track, and the ride still had major problems. The ride was a (very cool looking) lemon. I doubt SF saw any reason to prolong the inevitable by updating LIM's on a ride that had just as many problems in other areas. It all comes down to $$$.
Someone else covered GASM's maintenance issues and costs succinctly. Although I do think in addition to expensive replacement parts they were also having to weld stress fractures more often than they would've liked. I'm not certain on that though. As for the ride it gave, look, I'm willing to forgive some roughness. I actually love Ninja @ SFOG. I know it's rough and a major headbanger, but I love it because it's unique, and despite the roughness I have fun on it. GASM was rough, and just not that special of a ride, and I didn't have fun on it. I wanted to like GASM, I really did. When it first came out I was obsessed with it, and when I finally got to ride it in 2008 it was a bit like a childhood wish coming true. But at the end of the day it was just another headbanging Arrow megalooper. Notice how those seem to be disappearing more and more? There's a reason for that. As for "knowing how to ride" GASM? I see that phrase come up for a lot of rough rides that people are defending. Not entirely sure I buy it. Shouldn't I be able to just ride it without having to do an elaborate interpretive dance from within my restraint just to keep from banging my noggin into oblivion?
I like the GIB's, and think one would've been a top-tier "filler" ride for our park until we could've gotten something new. But I see your point on it. As for Chang, it would've been great for our park imo.
A few pages back I also said I would prefer we get nothing this year (if it's going to be a Boomerang), and wait a year or two for something more substantial. So we're on the same page on that one. And I agree that a Boomerang will do nothing to bring people into the park. Look at how great American Thunder is, yet when you talk to locals they're still very much fixated on The Boss. Our park needs something BIG to really get people excited about the place.