short version:
Upgrading libncurses5 breaks the Debian image and Maemo's Easy Debian installation.

long version:
When I started using ED Lenny was still stable and I prefer to use a pure Debian stable. However Squeeze was already in freeze for some time and I thought upgrading the whole ED installation to Squeze should be a good idea. So I upgraded to Squeeze but ED froze during the upgrade. I had to kill it from Maemo.
When trying to restart ED via the launcher icon it didn't start, so I tried from a terminal. Unfortunately I don't remember the error message but basically it was saying that Maemo's ED was broken. So I reinstalled ED and tried again. ED started but from within Debian I received an error message about a broken libncurses.so.5 and I didn't even get to a console login. I couldn't fix this with fsck. The image was broken so I had to restore my backup from before the dist-upgrade.
My image was highly customized at that time so I thought that there might be a problem with some dependencies. I tried a 2nd time with a vanilla ED image but got the same libncurses5 problem. Then I tried a 3rd time with an image that was pretty much stripped down to only run LXDE, but the problem still existed. Unfortunately one can't get rid of libncurses5 if one wants to keep a working Debian.

I'm fine with Lenny as long as it gets support, but I don't like release mixes. You always have to watch out for dependency problems.
Frankly I was pretty shocked when I had the first look at ED's sources.list: Lenny + Squeeze + multimedia for both releases. I figured out that multimedia was necessary for working audio, but I'd prefer to have only one release in there.

btw:
Does anybody know why audacity crashes when stopping a playback? Until then it works fine but both, the versions from Lenny and Squeeze crash when clicking the stop button. Unfortunately I have no other ARM system to check if this is a bug in the Debian package.