Lest it have not shown well enough my comment about 68000 Macs was tongue-in-cheek. Of course they run software of the appropriate scale and vintage well enough... although I suppose to be honest the Macintosh was rarely described as being a "fast" machine even at the time. (Contemporary software reviews often describe the 8Mhz Macs as being about as fast as 4.77Mhz IBM PCs for doing a given task... which means of course the hardware is faster because in addition to doing the task itself it's running a GUI. But it did mean a similarly clocked 80286 PC AT could run rings around a Mac in a task like recalculating a spreadsheet.) I was only underlining my point was that if you're expecting an old machine to live up to a new one you're going to be disappointed.
Computer years are far shorter than dog years, so adding just a few years can mean a several-fold decrease in capability. And, sad to say, you'll see this even if you run period software. Take normal everyday tasks like a loading 200k document or manipulating a color image file which uncompressed occupies a megabyte or two of RAM. A modern mass storage device and CPU can handle tasks like that essentially instantaneously, while loading or saving a few hundred K or performing some sort of transform on a moderately-sized framebuffer will take a perceptible amount of time on an old system, no matter how efficient the software is. Undoubtedly any given old computer felt "fast" when it was born because those perceptible delays were that much more perceptible on the last computer its user owned... or if it was the person's first computer having it at all seemed like a quantum leap compared to breaking out the typewriter and slide rule. Unfortunately for the perception of these old machines time moves forward rather than backwards.
Remember when it "mattered" how fast a given web browser would render a page? People used to go crazy obsessing over side-by-side speed tests, because it did matter how efficient the rendering engine was when we were still running double-digit-Mhz-speed CPUs. Some still do, I guess, but... come on, on a new-ish computer *any* web browser can render a simple web page faster than your network connection can give it to you unless you're sitting behind an OC-48. Now the thing that matters is whether that computer is fast enough to handle the latest Flash video standard or amazingly inefficient HTML5 animation. Nobody even *thinks* about how long it should take to load a 200k Word document simply because it doesn't take any time anymore.
When you fire up your LC 575 you're activating up a time machine. Enjoy it! Or don't.