Do not turn on Smart Reflex. Consider it lucky when you only experience lag.
After you have rebooted does ti still lag? IMO swappolube might give you instant boost but in long run nobody knows how it works with multiple different memory scenarios. Also if device lags in certain time of day you might want to check how to disable 24h cycled update checker. Use power search and maemo wiki for more infromation.
gconftool -s -t int /apps/hildon/update-notifier/check_interval 1440000