Thanks to the Qt/KDE team, specially to Maxy who has done most of the packaging and uploading, sid users are now enjoying KDE 4.10.5, including the new KDE PIM stuff that we have held out for the Wheezy release.
I started using KMail2 (inside Kontact) a few days after Wheezy's release, getting it from experimental. And I have to admit that I really like it, just like with KMail1.
But my upgrade did have some bumps on the road, so I'm sharing them here so you can now how I solved them.
Mail import worked as we were waiting: it did work. So it was really useful to hold back Kmail1 until this really worked.
Now, I had a problem with my hard disk: whenever KMail started, it would start accessing it without pause. There where two reasons (for what I could test, I haven't looked at the source to really see if there was some other oddity) for this: I had a nepomuk/virtuoso DB created quite some time ago and initial mail indexing.
The initial mail indexing takes lots of time. For 1GB of DIMAP I had to wait like 5 hours (yes, 5 hours) on a 5600 rpm disk to let it fully finish. My desktop machine, with a faster hard drive, took a little less.
As far as people told me, that should have been enough, but my disk kept crawling. So I remembered someone from the team saying something about people with early-created nepomuk/virtuoso databases will have some speed issues. Mine where more than that, buy trying was worth the shot.
I had nepomuk disabled since I tried it the first version due to this exact problem. So I closed my KDE session and removed the nepomuk/virtuoso data:
rm -r ~/.kde/share/apps/nepomuk/
Then I logged back in KDE and waited (again) the 5 hours to let nepomuk re index my mail, this time totally finishing after 5 hours. Starting from that point, I get some one or two minutes of disk trashing some times I log in (not always), but it's actually not that bad. And I heard that in KDE 4.11 this has been improved a lot, so I should see a better behavior from that point on.
Please understand that this was my trial-and-error fix, it may be possible that someone comes with a better solution :-)