The main difference between org.maemo.fremantle vs com.nokia.meego is related to workarounds against bugs is qt 4.7.0.
org.maemo.fremantle MUST run with reaster qt graphics engine, while com.nokia.meego SHOULD be run with opengl graphics engine. (and only by CSSU users, remember)

• fremantle components use Qt 4.7 namespace (they don't depend on qtquickcompat package)
• fremantle components don't have magnifier (opengl segfault)
• fremantle users can't use 'action key' (with SipAttributes component) on Maliit VKB (qt segfault)
• fremantle users can't use opengl with progressbar (qt segfault)

I still wonder why Nokia didn't push a Qt 4.7.3 or 4.7.4 on oficial firmware...