This Clown's blog has posted a review of Private Lives and had some very complimentary comments to make about the show and all the actors.  Make sure to read the whole review HERE.
Here's what he had to say about Matthew Macfadyen:
"MacFadyen  matched her though, with his waspish delivery of some great zingers,  some nifty piano-playing and unafraid to show some vulnerability beneath  the suave, disaffected, handsome exterior. And together they [Matthew and Kim Cattrall] display  great chemistry, turning on a dime from pure comedy to impassioned  anger, from sexual energy to gentle crooning over the piano, I totally  bought them as a couple who couldn't live without each other, yet drove  each other up the wall."