Pros
This is the company where I spent the 10 best years of my career so far. Lately (in the last 4 years or so), I could really see how Yahoo's aggressive bets on innovation really put them in the path to success, e.g.: Hadoop, OpenStack, HTML5, Isomorphic / Single Page Apps. Now I'm cheering for them from the sidelines, and I hope to see them succeed. I'm also grateful for a lot the people that I got to interact with during my stay there, all the cool and new technologies that I got to work on/with, and all the things that I learned.
Cons
Once you end up in a team where either a) the manager doesn't like you, or there is just no chemistry between you and the manager, or b) the manager already has a chosen set of favorite people that they know really well and have strong trust relationships with (and getting a new manager like that could happen any day given the huge amount of re-orgs taking place over there all the time)... it will be only a matter of time before you will start getting bad "QPR" ratings, with all the stress and reduced options (even moving to other positions becomes harder once you get a bad "grade") that that brings. All this is too much stress and too little to gain, if you ask me, which is unfortunate given all the good things that the company has going for it.