I've been using libmoto since OS 7.6, all the way until now, OS 9.0.4, and have never experienced problems related to it, until recently. Upon removal, I first noticed slightly faster boot up, and faster response in the Finder. I also regained prior stability in said apps. The strangest effect was Netscapes speed, which appeared to have doubled.
Pages load almost twice as fast, and java seems to startup quicker.
How an extension that replaces a few math routines causes so much trouble still bewilders me. And to tell the truth, the only time I saw a significant performance boost from libmoto was when I used to play Doom and Marathon on my IIci. As noted below, the primary gain seen from Libmoto was boosting MacBench FPU scores, and there were other issues noted even in older OS versions and some games. Last year the same problems were reported here in 1997 with the original Carmageddon game. The only time I enabled it is to compare Macbench scores with a past submission that used Libmoto, I'd never use it otherwise.