Vantaggi
Microsoft remains a great place to have an impact on work done by millions through our products. It also offers competitive compensation and excellent benefits (particularly the health insurance which really means you pay nothing for all your care including perscriptions). It has grown dramatically in the 10 year I've been there and has handled some of the growth well (keeping great benefits). Microsoft remains Redmond focused, but is getting much better at this issue. There is much more openness to people (including software developers) being located places other than Redmond. Silicon Valley is a major and growning location and Boston is growing too.
Svantaggi
It is a huge company with a bunch of bureaucracy, but this can be overcome if you work the system correctly. Despite a huge amount of construction, there continues to be a significant shortage of office space in the Redmond and Seattle area. This means that some people need to double up in offices which are meant for only one. Some times groups are not as coordinated as they should be and sometimes decisions take too long to get. However, if you make a good case, you can get major projects funded and resources assigned to try to make them realities.