I did not see or hear much problems with the new improved apt, apt-get , aptitude, etc. in Sid-unstble. I noticed much less output on the screen after apt-get dist-upgrade of those programs in sid and now also here in sparky.
In the dist-upgrade it will warn of the new defaults for apt- pinning. If you do have a few or lots of programs "pinned" to specific versions you might want to investigate more before you dist-upgrade. In general, in testing and sid, whenever you see programs involved in the upgrade process being upgraded, it is good to check out the debian bug pages for those programs.
My opinion is a strong round of applause to the Debian APT Development Team.