1. GPLv2 will remain as is and programs have the option of remaining under that license.
2. GPLv2 and GPLv3 code cannot be combined to form a new program. But GPLv2 and GPLv3 programs can coexist together on a system.
3. GPLv3 will block the "tivoization" of computers. TiVo uses GPL covered software, but the appliance shuts down when it detects modified software.
4. It ensures you are free to remove the handcuffs imposed by DRM. In Stallman's words
"..it makes sure that you are just as free to remove nasty features as the distributor of your copy was to add them."5. It also resists the threat of patent deals like Novell-M$ deal. Releasing a program under GPLv3 protects it from future Microsoft's future attempts to make redistributors collect royalties from program's users.
6. It provides for explicit patent protection of the users from the programs contributors and re-distributors.
7. Further advantages of GPLv3 include better internationalization, gentler termination, support for BitTorrent, and compatibility with the Apache license.
Stallman has this dream of getting software patents abolished or protect users from them so as to render the patents void.. Software patents are nasty alright, it has this capacity to dull creativity and to a large extend throttle software evolution.
Quoting from the article by Stallman:
The only way to make software development safe is to abolish software patents, and we aim to achieve this some day. But we cannot do this through a software license. Any program, free or not, can be killed by a software patent in the hands of an unrelated party, and the program's license cannot prevent that. Only court decisions or changes in patent law can make software development safe from patents. If we tried to do this with GPLv3, it would fail.