Pros
The company has been humbled for the second time: first, 2001, then 2008. So you'll find much less of that corporate jock culture or 'unquestionable geniuses'. This time, particularly, asking hard wquestions has no been frowned upon anymore. The company is trying to make it big in the internet once again, so, if you're lucky, you'll be able to have a say in an important decision that will potentially affect millions of users. Well, if things don't work out in the end, at least you'll have learnt something. Yahoo!'s benefits are in line with the top in its industry, and that includes Google. From what I saw, salaries at Yahoo! are higher.
Cons
This is a beleaguered internet company, no questions about it, so you may face tough times if things go sour. The company got in this situation by itself, and you'll be able to see why if you work here. Resistance to change, indecision, lack of support, pointless internal competition, and other well known corporate vices can be found here, but that doesn't make for a terrible atmosphere.