There is a great article by Gaia Clary in the SL Forum: Blender 2.68: Weight Tools reworked. She is explaining how weight painting in Blender has improved. Tools work as one intuitively thinks they should. I see that as a big improvement. I’ve fought with Blender weight painting for some time.
Also the documentation has been updated. See the Vertex Groups section of the 2.6 manual.
Blender comes in 32 and 64 bit versions. The Archive version is far easier to install.
Campbell Barton and Gaia worked to get the weight painting documented and fixed. The fixes are only in the release candidates. Get a copy and try it. Find bugs and report them in the Blender bug reporter. They expect to release 2.68 in 2 weeks. So, if there are problems, we need to find them ASAP.
The release notes are here. They are an obvious work in progress.