I've ran the Waves Ltd. CLA-3A on a few different systems, but not only until recently did I have it running on my home system. I've ran it on two different Pro Tools HD systems at professional studios, but right now at home I'm running it in Pro Tools LE 8. I run it on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I'm running Pro Tools with a Digi 002 rack version or a Digidesign Micro Box depending on if I'm at home or on the go. Within this configuration I haven't had any performance issues running the plug-in, as I can run a few of them at a time without a problem.
I like using the Waves Ltd. CLA-3A as it gives me a familiar interface to work with, even if it doesn't sound quite like a real LA-3A. If you're expecting this, you're expecting too much. However, the plug-in is a nice compressor in it's own right even if it doesn't live up to it's name. It's great for guitars and drums I find, although there are definitely other compressors in my plug-in suite that I'll look to before this one. In fact, while it's comparable in sound quality to the other plug-ins in the Classic Compressors bundle, it's probably not my favorite of the bunch. You can't buy this plug-in on it's own, so if you're interested you'll have to be looking at the full Classic Compressor bundle or the Waves Complete bundle. Either way, the CLA-3A is definitely a plug-in worth knowing about and trying whenever possible for you.