thanks to qgil, Stskeeps, w00t and qwazix for your clarifications about Qt 5 on Maemo 5 and the development of Maemo in general.
even though having been using KDE pretty much since the beginning (at least on GNU / Linux), i'm not much of a OS / Framework developer, alas
played with the thought of creating some simple Qt widget to display system stats (mostly temperatures) but at the end of the day, holding the N900 in your hand tells you right away whether some process went rogue & is frying the CPU
guess i will try & get Nemo running on my spare N900 & see where that goes...