Interesting topic.
Stevie - My favorite vocal period for her was Tusk through Mirage era (with Bella Donna being the zenith for me). She's been hit or miss with me since vocally. I also feel her songwriting has been inconsistent (I thought her SYW material was pretty weak, overall), but I was impressed with IYD. She's settled into this "icon" thing pretty well, and I'm happy to see that.
Lindsey - I feel Lindsey's songwriting is the strongest it's ever been, by leaps and bounds. What would have been the original GOS were his best lyrics, ever. Guitar playing is still great. Vocally, he's slipped a notch. And I'm no singer or music expert, but some of his live vocals sound way off to me.
Christine - Not much to go on here, although she sounded wonderful on ITM.
John - Sounds good to me.
Mick - He's definitely lost something, innovation and what not, though he's still very capable.