During the past few years I have been nearly the only one answering questions on this forum. In order to get faster and more thorough answers, it thus recommended to use other more active channels:

• To ask for help, better use stackoverflow. I also follow the eigen tag on stackoverflow, so no need to post the same question twice, and as a bonus you will reach many more users who are willing to provide answers and you will benefit from experts in various other areas (e.g., Visual, cmake, iOS, etc.).
• To report bugs, better use our bug tracker. This way, all Eigen's developers will be aware of the issue, and it won't be lost until it is fixed.
• To discuss with developers, of Eigen's design and future features, better use our mailing list.

And of course, before posting, make a search within this forum and stackoverflow!