Just some corrections and personal opinions :P
1. The recent xModules (xPaintClass, xStatsClass, xLabel, xTaskbar, xPopup and xTray) are "FINAL" versions, that means no real further development is planned and NO remaining (reported and reproducable) bugs are left!
2. xPaintClass (and xStatsClass) are NO modules!
They are "core" dll's like lsapi.dll, that means they contain stuff, but they don't do anything.
Therefore, if we would have a recent "official" installer they would be automatically installed in the Litestep folder and there wouldn't be problem at all.
They CAN be loaded as modules, to ensure that themes can download them automatically via NetloadModule and therefore work on not recent Litestep installations without xPaintClass in the Litestep folder.
3. xStatsClass was seperated from xLabel due to requests from themers (smaller xLabel without the text stats stuff).
4. xStatsClass isn't required for xLabel to run (since xLabel version 4.0.6).
5. xPaintClass has no bugs! (The update(s) i have released contain only further enhancements for perfectionists)

I don't mention the advantages of xPaintClass, since i have done it many times before.

@xcal:
If you don't theme anymore, because of xPaintClass, then it is your decision, but you really miss some nice features and visual improvements. :P
And themeing isn't more complicated because of xPaintClass, only 1! additional setting is required compared to older versions and that is the ...PaintingMode setting. On the other hand the few changed settings are much more logical (and shorter) then before.
I really like critical opinions or suggestions for improvements, but i still cannot see the problems, you see.
Sorry :)

Andymon