Since a channel strip is something I'd want to use on most if not all tracks, I'd say versatility, stability, and low CPU hit are musts. It also has to sound good, of course. The
Metric Halo fits that bill nicely.
I love the Abbey Road plugins, but they hammer my poor CPU. I use them on particular tracks or buses.
For those looking for an inexpensive console-style strip,
TBProAudio has a new one that's been getting some good reviews.
Cheers,
Eddie