Pros: - many production quality features
- highly polished
- small download
- large support community, with very active development
- open source and free!
- integrates with other 3D software formats and software (incl renderers, etc)
Cons: - interface can be quite daunting (but nothing tutorials and playing around can't solve)
- beta version might present some small bugs
Other Thoughts: As a graphic design student, I'm using Blender right now to learn the basics of 3D modelling. I'm impressed with the fact that this free program of less than 60mb can compare with the might of Maya. After I get more to grips with both programs, I might even consider doing modelling in Blender, and only exporting to Maya for rendering.
But overall, I'd highly recommend Blender for anyone that has played around in Sketchup/123D Design and wants something more advanced.