Eh, I like Marissa, and I've worked on projects (the 2010 websearch visual redesign, and doodles) for which she was the executive sponsor. No, she's not a nice person, and most likely she does not give a shit about you as a person. But she is very often right about her design opinions, and when she's not, she'll listen to data.
I don't think Yahoo particularly needs a nice person as CEO right now. Their culture is dysfunctional enough that they probably need a Steve Jobs type, someone with clear opinions who's willing to ruffle a lot of feathers (and make a bunch of people quit). Steve Jobs wasn't really a nice person either.
I've worked at both Yahoo and Google. I've never worked with Marissa directly but I think your opinion of her is pretty much correct.
The biggest risk I see is that there is a huge difference in her role. At Google she stood atop a pyramid of other geniuses, with similar backgrounds and values, and was a filter for their ideas. At Yahoo she's dealing with a culture where engineering is not the highest value, and she's going to have to get off the top perch and descend into the ranks, clearing out the enemies of progress which exist at every level.
I disagreed with nearly everything I ever heard Marissa say related to design, especially her over reliance on A/B testing to inform design. I think she is one of the main reasons Google products tend to feel like they are designed by engineers.
Their products are usable and uncluttered. I have reservations about the new unified look (too much padding in horizontal stripes one can't scroll, trying to displace browser chrome), but I've been very happy with the previous, “designed by engineers” Google aesthetic.
There are so many UX problems with the current crop of Google core products, it's hard for me to agree that "usable and uncluttered" can refer to anything but the Google of the past.
What's wrong with relying on A/B testing to inform design? In my opinion, except for the whole Google+ unifying process going on most Google products are highly usable.
Most observers seem to agree that Yahoo's problem is cultural in nature. It's not a Nokia-esque situation, where the company was heavily damaged by competitive forces before Elop even showed up.
A big part -- a necessary part -- of the way Jobs changed the culture at Apple was by bringing in a lot of people who had been loyal to him for years at Next and elsewhere. I can't think of any cases where an outsider has parachuted into a large company, by invitation or otherwise, and turned it around by himself/herself.
Can/will Mayer do that? If so, where will the required team of revolutionaries and revanchists come from? If she doesn't (or can't) raid Google, then where will she get the people she will need?
There're lots of good people at Yahoo. I've heard from other Google engineers who do a lot of interviewing that their recent impression of a lot of ex-Yahooers has been "Hire this person NOW. How could the company let someone like this go?"
I wouldn't be terribly surprised if one of Marissa's first moves is to fire all the middle management and then promote a bunch of longtime individual contributors into their place.
I don't think Yahoo particularly needs a nice person as CEO right now. Their culture is dysfunctional enough that they probably need a Steve Jobs type, someone with clear opinions who's willing to ruffle a lot of feathers (and make a bunch of people quit). Steve Jobs wasn't really a nice person either.