The TC Electronic Tube Tech CL 1B is a plug-in version of this Tube Tech hardware. I had no compatibility issues at all and it has always run pretty flawlessly for me. The interface of the plug-in is incredibly accurate when compared to the hardware version of the CL 1B, and everything is easy to access and understand. You've got knobs for gain, ratio, release, attack, and threshold. It then has a programmable meter a few other switchable knobs. I don't have the manual for this plug-in, but it is easy enough to use that I never needed it.
I am currently running TC Electronic Tube Tech CL 1B plug-in on a Pro Tools HD System that runs off of an HD 3 Accel card, a Digidesign 192 I/O audio interface and an Apple Mac G5 computer. I've never had a problem running a few of these at once on this system, and I've probably had five or six of these up at once without any issues. It really depends on your personal set up how many of these your system can handle at once.
I've been using the TC Electronic Tube Tech CL 1B plug-in for about a year and have found it to be a great substitution when I don't have access to a real Tube Tech CL 1B. I love plug-ins that are modeled after real gear because they are easy to use if I have already used the hardware version, which is the case with this plug-in. The price of this plug-in is more expensive than I believe it should be, which is really this plug-ins only problem. Beyond this, it runs smoothly and really has a great sound quality. While it doesn't sound as great as a real Tube Tech CL 1B (and I believe no plug-in is as good as the real thing), this is a good emulation and is definitely worth having in your arsenal.