Still very much like+use this plugin!
One question: when loading a youtube track via yttm, the youtube playcount is not shown anymore (which I used for an additional filter via the Skip Track plugin).
When loading the same youtube track directly via foo_youtube, the playcount is available, as shown in the comparison of the properties of the identical youtube track below.
Any hint on how to get the playcount as well with the YTTM plugin?

I presume you mean the view count, rather than playcount as the only playcount in the pics is 0 in both cases.

View count, and population of the Youtube source fields, is handled by the foo_youtube plugin and so a fix likely requires a bug fix in the foo_youtube plugin itself. For info, there is some difference in handling between loading by YTTM and standard direct loading, i.e. script uses the metadata overriding feature, so artist & title etc are correct, and so the bug likely relates to that. In my tests, the current behaviour is erratic: sometimes view count is present with those sent by YTTM, other times it's missing.

If you really mean view count, then consider pointing 3dyd at this thread to see if it can be fixed.