That's great! Aapo, could you please SSH into your N900 while a scenario is running in Lincity-ng and monitor the CPU usage with top? I'm particularly interested in the figures for Lincity-ng itself, Xorg and pulseaudio. Also is your N900 overclocked?
%MEM %CPU 43.0 66.7 /opt/lincity/games/lincity-ng -f -s -S 800x480 1.2 11.3 /usr/bin/pulseaudio --system --high-priority 5.0 2.3 /usr/bin/Xorg -logfile /tmp/Xorg.0.log -logverbose 1 -nolisten tcp -noreset -s 0 -core