There will not be Debian packages for KDE 4.1 beta 2. Last week, beta 1 was replaced in experimental by a snapshot of the revision 819867, and beta 2 was tagged at revision 821791, so it is not a huge difference.
I have no idea when we will do the next update for the KDE 4.1 packages, I guess with the RC 1. My personal plans for the next 2 weeks are polishing all the possible KDE 3.5.9 for Lenny.
The instructions I blogged about how to install KDE 4.1 beta 1 still apply, the only changes are: extragears-plasma package is now called kdeplasmoids and the version is 4.0.82+svn819867 instead of 4.0.80.
In the case you are installing in a clean environment, you can use directly the metapackages: kde4-minimal for a minimal KDE 4 environment: kdelibs, kdepimlibs and all the kdebase packages; or kde4 that will install everything.
As important note, if you are using these packages, remember before reporting a bug that the issue could be already fixed in the beta 2 or later.
And, by the way, hi planet KDE!