yup in your case, I'd go with the upgrade. I'm going for the low end model in October but I won't be doing any video editing at all.... just using it as an itunes library/web surfing/ skype/ mail...
i'd love an extra £100 to get the upgrade but I'm really tight on cash!
PS anyone know if the HD 2400 has any encoding hardware that might speed up my Handbrake encoding against my 2.0ghz core 2 duo macbook?