I've been using UAD's Fairchild Tube Limiter Collection on a recent project and have come to appreciate the enhancements and differences between them and the original Fairchild Limiter plugin.
From the website:
"In 2004, Universal Audio released the Fairchild 670 Legacy plug-in, which was quickly heralded as the best 670 emulation available. Today, UA’s team of DSP experts have improved the original Time Constants and gain reduction curves, while modeling — for the first time ever — the complete tube-powered amplifier and transformer sections of their hardware counterparts. Far beyond other Fairchild emulations, only the new UAD Fairchild Collection is based on accurate circuit models of Ocean Way Studios' “golden-reference” units."
Fairchild Limiter Collection Features
Here'a a video by UAD with some great tips on using the Fairchild collection to enhance your songs:
The Fairchild Tube Limiter Collection is currently on sale for $149 (reg. price $299).